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 $88.97   8.540%   $96.568   $96.57   $96.55   $96.60  
  Purchase #2 $52.53   5.555%   $55.448   $55.45   $55.45   $55.40  
  Purchase #3 $231.61   4.827%   $242.7898   $242.79   $242.80   $242.80  
  Purchase #4 $50.45   3.428%   $52.1794   $52.18   $52.20   $52.20  
  Purchase #5 $213.40   3.307%   $220.4571   $220.46   $220.45   $220.50  
  Purchase #6 $149.27   13.673%   $169.6797   $169.68   $169.70   $169.70  
  Purchase #7 $227.89   7.461%   $244.8929   $244.89   $244.90   $244.90  
  7 purchase totals = $1,014.12       $1,082.0149   $1,082.02   $1,082.05   $1,082.10