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 $89.96   5.568%   $94.969   $94.97   $94.95   $95.00  
  Purchase #2 $235.54   10.301%   $259.803   $259.80   $259.80   $259.80  
  Purchase #3 $72.30   5.772%   $76.4732   $76.47   $76.45   $76.50  
  Purchase #4 $99.76   8.351%   $108.091   $108.09   $108.10   $108.10  
  Purchase #5 $110.74   9.656%   $121.4331   $121.43   $121.45   $121.40  
  Purchase #6 $116.77   10.312%   $128.8113   $128.81   $128.80   $128.80  
  Purchase #7 $203.60   7.706%   $219.2894   $219.29   $219.30   $219.30  
  7 purchase totals = $928.67       $1,008.8700   $1,008.86   $1,008.85   $1,008.90