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 $118.36   6.416%   $125.954   $125.95   $125.95   $126.00  
  Purchase #2 $69.92   7.858%   $75.4143   $75.41   $75.40   $75.40  
  Purchase #3 $232.71   9.484%   $254.7802   $254.78   $254.80   $254.80  
  Purchase #4 $99.28   6.661%   $105.893   $105.89   $105.90   $105.90  
  Purchase #5 $149.50   12.370%   $167.9932   $167.99   $168.00   $168.00  
  Purchase #6 $180.37   6.228%   $191.6034   $191.60   $191.60   $191.60  
  Purchase #7 $213.28   8.347%   $231.0825   $231.08   $231.10   $231.10  
  7 purchase totals = $1,063.42       $1,152.7206   $1,152.70   $1,152.75   $1,152.80