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 $92.60   5.132%   $97.3522   $97.35   $97.35   $97.40  
  Purchase #2 $107.29   6.116%   $113.8519   $113.85   $113.85   $113.90  
  Purchase #3 $189.45   3.289%   $195.681   $195.68   $195.70   $195.70  
  Purchase #4 $180.26   6.313%   $191.6398   $191.64   $191.65   $191.60  
  Purchase #5 $222.50   5.857%   $235.5318   $235.53   $235.55   $235.50  
  Purchase #6 $130.40   11.586%   $145.5081   $145.51   $145.50   $145.50  
  Purchase #7 $95.97   6.699%   $102.399   $102.40   $102.40   $102.40  
  7 purchase totals = $1,018.47       $1,081.9638   $1,081.96   $1,082.00   $1,082.00