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 $190.97   7.633%   $205.5467   $205.55   $205.55   $205.50  
  Purchase #2 $149.93   7.342%   $160.9379   $160.94   $160.95   $160.90  
  Purchase #3 $241.35   10.607%   $266.95   $266.95   $266.95   $267.00  
  Purchase #4 $89.98   8.139%   $97.3035   $97.30   $97.30   $97.30  
  Purchase #5 $172.26   6.701%   $183.8031   $183.80   $183.80   $183.80  
  Purchase #6 $114.25   10.603%   $126.3639   $126.36   $126.35   $126.40  
  Purchase #7 $24.78   5.237%   $26.0777   $26.08   $26.10   $26.10  
  7 purchase totals = $983.52       $1,066.9828   $1,066.98   $1,067.00   $1,067.00