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 $118.80   5.835%   $125.732   $125.73   $125.75   $125.70  
  Purchase #2 $63.72   6.166%   $67.649   $67.65   $67.65   $67.60  
  Purchase #3 $239.51   5.769%   $253.3273   $253.33   $253.35   $253.30  
  Purchase #4 $38.82   13.355%   $44.0044   $44.00   $44.00   $44.00  
  Purchase #5 $126.31   8.380%   $136.8948   $136.89   $136.90   $136.90  
  Purchase #6 $184.34   9.603%   $202.0422   $202.04   $202.05   $202.00  
  Purchase #7 $182.27   12.289%   $204.6692   $204.67   $204.65   $204.70  
  7 purchase totals = $953.77       $1,034.3189   $1,034.31   $1,034.35   $1,034.20