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 $43.42   9.498%   $47.544   $47.54   $47.55   $47.50  
  Purchase #2 $56.72   12.494%   $63.8066   $63.81   $63.80   $63.80  
  Purchase #3 $66.43   10.481%   $73.3925   $73.39   $73.40   $73.40  
  Purchase #4 $212.62   5.207%   $223.6911   $223.69   $223.70   $223.70  
  Purchase #5 $198.62   6.212%   $210.9583   $210.96   $210.95   $211.00  
  Purchase #6 $243.32   11.550%   $271.4235   $271.42   $271.40   $271.40  
  Purchase #7 $247.98   10.797%   $274.7544   $274.75   $274.75   $274.80  
  7 purchase totals = $1,069.11       $1,165.5704   $1,165.56   $1,165.55   $1,165.60