Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $153.75   8.780%   $167.2493   $167.25   $167.25   $167.20  
  Purchase #2 $113.33   10.471%   $125.1968   $125.20   $125.20   $125.20  
  Purchase #3 $109.94   13.861%   $125.1788   $125.18   $125.20   $125.20  
  Purchase #4 $155.32   10.489%   $171.6115   $171.61   $171.60   $171.60  
  Purchase #5 $241.53   9.196%   $263.7411   $263.74   $263.75   $263.70  
  Purchase #6 $235.31   5.207%   $247.5626   $247.56   $247.55   $247.60  
  Purchase #7 $149.47   12.322%   $167.8877   $167.89   $167.90   $167.90  
  7 purchase totals = $1,158.65       $1,268.4278   $1,268.43   $1,268.45   $1,268.40