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 $188.63   6.840%   $201.5323   $201.53   $201.55   $201.50  
  Purchase #2 $91.60   5.844%   $96.9531   $96.95   $96.95   $97.00  
  Purchase #3 $55.52   12.144%   $62.2623   $62.26   $62.25   $62.30  
  Purchase #4 $243.30   6.258%   $258.5257   $258.53   $258.55   $258.50  
  Purchase #5 $42.87   6.419%   $45.6218   $45.62   $45.60   $45.60  
  Purchase #6 $215.59   6.826%   $230.3062   $230.31   $230.30   $230.30  
  Purchase #7 $173.60   6.671%   $185.1809   $185.18   $185.20   $185.20  
  7 purchase totals = $1,011.11       $1,080.3823   $1,080.38   $1,080.40   $1,080.40