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 $194.78   4.847%   $204.221   $204.22   $204.20   $204.20  
  Purchase #2 $23.89   12.544%   $26.8868   $26.89   $26.90   $26.90  
  Purchase #3 $194.82   5.725%   $205.9734   $205.97   $205.95   $206.00  
  Purchase #4 $167.86   11.635%   $187.3905   $187.39   $187.40   $187.40  
  Purchase #5 $82.30   4.351%   $85.8809   $85.88   $85.90   $85.90  
  Purchase #6 $191.85   5.701%   $202.7874   $202.79   $202.80   $202.80  
  Purchase #7 $98.91   11.761%   $110.5428   $110.54   $110.55   $110.50  
  7 purchase totals = $954.41       $1,023.6828   $1,023.68   $1,023.70   $1,023.70