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 $113.49   10.795%   $125.7412   $125.74   $125.75   $125.70  
  Purchase #2 $147.37   3.849%   $153.0423   $153.04   $153.05   $153.00  
  Purchase #3 $189.78   6.208%   $201.5615   $201.56   $201.55   $201.60  
  Purchase #4 $60.26   4.474%   $62.956   $62.96   $62.95   $63.00  
  Purchase #5 $233.85   8.476%   $253.6711   $253.67   $253.65   $253.70  
  Purchase #6 $92.52   8.106%   $100.0197   $100.02   $100.00   $100.00  
  Purchase #7 $148.52   12.272%   $166.7464   $166.75   $166.75   $166.70  
  7 purchase totals = $985.79       $1,063.7382   $1,063.74   $1,063.70   $1,063.70