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 $89.98   7.358%   $96.6007   $96.60   $96.60   $96.60  
  Purchase #2 $229.59   6.268%   $243.9807   $243.98   $244.00   $244.00  
  Purchase #3 $225.98   8.678%   $245.5905   $245.59   $245.60   $245.60  
  Purchase #4 $73.98   11.591%   $82.555   $82.56   $82.55   $82.60  
  Purchase #5 $221.68   7.743%   $238.8447   $238.84   $238.85   $238.80  
  Purchase #6 $227.44   4.598%   $237.8977   $237.90   $237.90   $237.90  
  Purchase #7 $119.85   5.846%   $126.8564   $126.86   $126.85   $126.90  
  7 purchase totals = $1,188.50       $1,272.3257   $1,272.33   $1,272.35   $1,272.40