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 $203.40   7.675%   $219.011   $219.01   $219.00   $219.00  
  Purchase #2 $180.82   13.548%   $205.3175   $205.32   $205.30   $205.30  
  Purchase #3 $49.46   6.350%   $52.6007   $52.60   $52.60   $52.60  
  Purchase #4 $138.30   12.410%   $155.463   $155.46   $155.45   $155.50  
  Purchase #5 $189.63   7.192%   $203.2682   $203.27   $203.25   $203.30  
  Purchase #6 $87.43   9.326%   $95.5837   $95.58   $95.60   $95.60  
  Purchase #7 $186.41   4.518%   $194.832   $194.83   $194.85   $194.80  
  7 purchase totals = $1,035.45       $1,126.0761   $1,126.07   $1,126.05   $1,126.10