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 $73.35   4.698%   $76.796   $76.80   $76.80   $76.80  
  Purchase #2 $68.56   10.798%   $75.9631   $75.96   $75.95   $76.00  
  Purchase #3 $97.35   6.424%   $103.6038   $103.60   $103.60   $103.60  
  Purchase #4 $159.67   6.662%   $170.3072   $170.31   $170.30   $170.30  
  Purchase #5 $223.86   5.257%   $235.6283   $235.63   $235.65   $235.60  
  Purchase #6 $199.80   11.453%   $222.6831   $222.68   $222.70   $222.70  
  Purchase #7 $190.89   11.817%   $213.4475   $213.45   $213.45   $213.40  
  7 purchase totals = $1,013.48       $1,098.4290   $1,098.43   $1,098.45   $1,098.40