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 $88.27   8.114%   $95.4322   $95.43   $95.45   $95.40  
  Purchase #2 $84.95   3.222%   $87.6871   $87.69   $87.70   $87.70  
  Purchase #3 $10.30   6.766%   $10.9969   $11.00   $11.00   $11.00  
  Purchase #4 $208.51   9.401%   $228.112   $228.11   $228.10   $228.10  
  Purchase #5 $69.71   7.115%   $74.6699   $74.67   $74.65   $74.70  
  Purchase #6 $156.98   6.157%   $166.6453   $166.65   $166.65   $166.60  
  Purchase #7 $87.52   10.432%   $96.6501   $96.65   $96.65   $96.70  
  7 purchase totals = $706.24       $760.1935   $760.20   $760.20   $760.20