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 $96.60   5.410%   $101.8261   $101.83   $101.85   $101.80  
  Purchase #2 $149.49   13.517%   $169.6966   $169.70   $169.70   $169.70  
  Purchase #3 $139.26   11.612%   $155.4309   $155.43   $155.45   $155.40  
  Purchase #4 $149.36   13.820%   $170.0016   $170.00   $170.00   $170.00  
  Purchase #5 $232.58   13.227%   $263.3434   $263.34   $263.35   $263.30  
  Purchase #6 $34.84   10.794%   $38.6006   $38.60   $38.60   $38.60  
  Purchase #7 $232.45   12.292%   $261.0228   $261.02   $261.00   $261.00  
  7 purchase totals = $1,034.58       $1,159.9220   $1,159.92   $1,159.95   $1,159.80