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 $53.42   10.162%   $58.8485   $58.85   $58.85   $58.80  
  Purchase #2 $142.54   6.350%   $151.5913   $151.59   $151.60   $151.60  
  Purchase #3 $61.68   6.857%   $65.9094   $65.91   $65.90   $65.90  
  Purchase #4 $111.29   13.249%   $126.0348   $126.03   $126.05   $126.00  
  Purchase #5 $192.89   6.130%   $204.7142   $204.71   $204.70   $204.70  
  Purchase #6 $234.85   6.356%   $249.7771   $249.78   $249.80   $249.80  
  Purchase #7 $219.42   11.643%   $244.9671   $244.97   $244.95   $245.00  
  7 purchase totals = $1,016.09       $1,101.8424   $1,101.84   $1,101.85   $1,101.80