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 $32.82   7.462%   $35.269   $35.27   $35.25   $35.30  
  Purchase #2 $168.91   8.799%   $183.7724   $183.77   $183.75   $183.80  
  Purchase #3 $102.74   5.129%   $108.0095   $108.01   $108.00   $108.00  
  Purchase #4 $96.37   8.363%   $104.4294   $104.43   $104.45   $104.40  
  Purchase #5 $95.69   8.818%   $104.1279   $104.13   $104.15   $104.10  
  Purchase #6 $185.92   13.350%   $210.7403   $210.74   $210.75   $210.70  
  Purchase #7 $217.85   8.206%   $235.7268   $235.73   $235.75   $235.70  
  7 purchase totals = $900.30       $982.0753   $982.08   $982.10   $982.00