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 $116.38   8.281%   $126.0174   $126.02   $126.00   $126.00  
  Purchase #2 $43.50   7.248%   $46.6529   $46.65   $46.65   $46.70  
  Purchase #3 $27.92   13.627%   $31.7247   $31.72   $31.70   $31.70  
  Purchase #4 $230.26   9.143%   $251.3127   $251.31   $251.30   $251.30  
  Purchase #5 $180.40   10.820%   $199.9193   $199.92   $199.90   $199.90  
  Purchase #6 $159.40   6.591%   $169.9061   $169.91   $169.90   $169.90  
  Purchase #7 $175.40   7.661%   $188.8374   $188.84   $188.85   $188.80  
  7 purchase totals = $933.26       $1,014.3705   $1,014.37   $1,014.30   $1,014.30