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 $88.39   7.465%   $94.9883   $94.99   $95.00   $95.00  
  Purchase #2 $99.84   10.765%   $110.5878   $110.59   $110.60   $110.60  
  Purchase #3 $235.86   8.856%   $256.7478   $256.75   $256.75   $256.70  
  Purchase #4 $164.92   10.555%   $182.3273   $182.33   $182.35   $182.30  
  Purchase #5 $152.55   4.566%   $159.5154   $159.52   $159.50   $159.50  
  Purchase #6 $213.27   8.752%   $231.9354   $231.94   $231.95   $231.90  
  Purchase #7 $244.86   10.765%   $271.2192   $271.22   $271.20   $271.20  
  7 purchase totals = $1,199.69       $1,307.3212   $1,307.34   $1,307.35   $1,307.20