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 $55.48   12.870%   $62.6203   $62.62   $62.60   $62.60  
  Purchase #2 $219.97   3.790%   $228.3069   $228.31   $228.30   $228.30  
  Purchase #3 $220.73   10.784%   $244.5335   $244.53   $244.55   $244.50  
  Purchase #4 $143.81   10.110%   $158.3492   $158.35   $158.35   $158.30  
  Purchase #5 $96.89   13.603%   $110.0699   $110.07   $110.05   $110.10  
  Purchase #6 $178.52   8.478%   $193.6549   $193.65   $193.65   $193.70  
  Purchase #7 $170.35   3.726%   $176.6972   $176.70   $176.70   $176.70  
  7 purchase totals = $1,085.75       $1,174.2319   $1,174.23   $1,174.20   $1,174.20