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 $41.97   10.202%   $46.2518   $46.25   $46.25   $46.30  
  Purchase #2 $196.86   11.766%   $220.0225   $220.02   $220.00   $220.00  
  Purchase #3 $33.52   5.279%   $35.2895   $35.29   $35.30   $35.30  
  Purchase #4 $183.54   9.562%   $201.0901   $201.09   $201.10   $201.10  
  Purchase #5 $47.53   5.845%   $50.3081   $50.31   $50.30   $50.30  
  Purchase #6 $233.80   10.738%   $258.9054   $258.91   $258.90   $258.90  
  Purchase #7 $223.28   9.662%   $244.8533   $244.85   $244.85   $244.90  
  7 purchase totals = $960.50       $1,056.7207   $1,056.72   $1,056.70   $1,056.80