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 $60.67   5.820%   $64.201   $64.20   $64.20   $64.20  
  Purchase #2 $143.36   4.140%   $149.2951   $149.30   $149.30   $149.30  
  Purchase #3 $240.72   10.569%   $266.1617   $266.16   $266.15   $266.20  
  Purchase #4 $211.96   9.184%   $231.4264   $231.43   $231.45   $231.40  
  Purchase #5 $120.41   7.634%   $129.6021   $129.60   $129.60   $129.60  
  Purchase #6 $43.95   10.546%   $48.585   $48.59   $48.60   $48.60  
  Purchase #7 $24.61   8.601%   $26.7267   $26.73   $26.75   $26.70  
  7 purchase totals = $845.68       $915.9980   $916.01   $916.05   $916.00