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 $141.73   5.660%   $149.7519   $149.75   $149.75   $149.80  
  Purchase #2 $76.81   12.194%   $86.1762   $86.18   $86.20   $86.20  
  Purchase #3 $182.87   9.685%   $200.581   $200.58   $200.60   $200.60  
  Purchase #4 $43.87   4.590%   $45.8836   $45.88   $45.90   $45.90  
  Purchase #5 $203.33   7.705%   $218.9966   $219.00   $219.00   $219.00  
  Purchase #6 $159.41   5.305%   $167.8667   $167.87   $167.85   $167.90  
  Purchase #7 $150.83   9.349%   $164.9311   $164.93   $164.95   $164.90  
  7 purchase totals = $958.85       $1,034.1871   $1,034.19   $1,034.25   $1,034.30