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 $57.92   10.205%   $63.8307   $63.83   $63.85   $63.80  
  Purchase #2 $203.95   3.776%   $211.6512   $211.65   $211.65   $211.70  
  Purchase #3 $95.89   8.504%   $104.0445   $104.04   $104.05   $104.00  
  Purchase #4 $132.86   7.472%   $142.7873   $142.79   $142.80   $142.80  
  Purchase #5 $141.86   9.632%   $155.524   $155.52   $155.50   $155.50  
  Purchase #6 $131.86   10.322%   $145.4706   $145.47   $145.45   $145.50  
  Purchase #7 $126.68   3.151%   $130.6717   $130.67   $130.65   $130.70  
  7 purchase totals = $891.02       $953.9800   $953.97   $953.95   $954.00