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 $215.71   7.811%   $232.5591   $232.56   $232.55   $232.60  
  Purchase #2 $219.41   6.298%   $233.2284   $233.23   $233.25   $233.20  
  Purchase #3 $115.62   3.419%   $119.573   $119.57   $119.55   $119.60  
  Purchase #4 $189.52   12.333%   $212.8935   $212.89   $212.90   $212.90  
  Purchase #5 $55.87   12.135%   $62.6498   $62.65   $62.65   $62.60  
  Purchase #6 $5.39   13.429%   $6.1138   $6.11   $6.10   $6.10  
  Purchase #7 $32.97   3.132%   $34.0026   $34.00   $34.00   $34.00  
  7 purchase totals = $834.49       $901.0202   $901.01   $901.00   $901.00