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 $43.46   5.751%   $45.9594   $45.96   $45.95   $46.00  
  Purchase #2 $238.78   3.299%   $246.6574   $246.66   $246.65   $246.70  
  Purchase #3 $88.33   10.198%   $97.3379   $97.34   $97.35   $97.30  
  Purchase #4 $192.67   4.833%   $201.9817   $201.98   $202.00   $202.00  
  Purchase #5 $57.46   3.113%   $59.2487   $59.25   $59.25   $59.20  
  Purchase #6 $20.59   13.254%   $23.319   $23.32   $23.30   $23.30  
  Purchase #7 $230.93   5.799%   $244.3216   $244.32   $244.30   $244.30  
  7 purchase totals = $872.22       $918.8257   $918.83   $918.80   $918.80