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 $182.90   13.277%   $207.1836   $207.18   $207.20   $207.20  
  Purchase #2 $94.77   13.853%   $107.8985   $107.90   $107.90   $107.90  
  Purchase #3 $163.54   9.402%   $178.916   $178.92   $178.90   $178.90  
  Purchase #4 $54.28   12.300%   $60.9564   $60.96   $60.95   $61.00  
  Purchase #5 $150.56   3.508%   $155.8416   $155.84   $155.85   $155.80  
  Purchase #6 $71.88   7.324%   $77.1445   $77.14   $77.15   $77.10  
  Purchase #7 $164.56   10.233%   $181.3994   $181.40   $181.40   $181.40  
  7 purchase totals = $882.49       $969.3400   $969.34   $969.35   $969.30