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 $86.80   11.704%   $96.9591   $96.96   $96.95   $97.00  
  Purchase #2 $59.36   6.616%   $63.2873   $63.29   $63.30   $63.30  
  Purchase #3 $232.77   4.791%   $243.922   $243.92   $243.90   $243.90  
  Purchase #4 $245.38   13.327%   $278.0818   $278.08   $278.10   $278.10  
  Purchase #5 $175.31   9.836%   $192.5535   $192.55   $192.55   $192.60  
  Purchase #6 $181.60   8.861%   $197.6916   $197.69   $197.70   $197.70  
  Purchase #7 $189.97   10.601%   $210.1087   $210.11   $210.10   $210.10  
  7 purchase totals = $1,171.19       $1,282.6040   $1,282.60   $1,282.60   $1,282.70