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 $58.65   6.600%   $62.5209   $62.52   $62.50   $62.50  
  Purchase #2 $158.74   11.170%   $176.4713   $176.47   $176.45   $176.50  
  Purchase #3 $201.87   11.444%   $224.972   $224.97   $224.95   $225.00  
  Purchase #4 $65.43   9.463%   $71.6216   $71.62   $71.60   $71.60  
  Purchase #5 $101.39   4.753%   $106.2091   $106.21   $106.20   $106.20  
  Purchase #6 $79.84   10.130%   $87.9278   $87.93   $87.95   $87.90  
  Purchase #7 $208.95   6.518%   $222.5694   $222.57   $222.55   $222.60  
  7 purchase totals = $874.87       $952.2921   $952.29   $952.20   $952.30