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 $186.69   4.459%   $195.0145   $195.01   $195.00   $195.00  
  Purchase #2 $211.31   3.757%   $219.2489   $219.25   $219.25   $219.20  
  Purchase #3 $153.39   11.166%   $170.5175   $170.52   $170.50   $170.50  
  Purchase #4 $244.66   12.836%   $276.0646   $276.06   $276.05   $276.10  
  Purchase #5 $153.62   3.571%   $159.1058   $159.11   $159.10   $159.10  
  Purchase #6 $149.34   4.449%   $155.9841   $155.98   $156.00   $156.00  
  Purchase #7 $55.38   5.763%   $58.5715   $58.57   $58.55   $58.60  
  7 purchase totals = $1,154.39       $1,234.5069   $1,234.50   $1,234.45   $1,234.50