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 $95.27   8.457%   $103.327   $103.33   $103.35   $103.30  
  Purchase #2 $44.40   9.434%   $48.5887   $48.59   $48.60   $48.60  
  Purchase #3 $97.59   7.446%   $104.8566   $104.86   $104.85   $104.90  
  Purchase #4 $197.92   11.276%   $220.2375   $220.24   $220.25   $220.20  
  Purchase #5 $170.51   11.304%   $189.7845   $189.78   $189.80   $189.80  
  Purchase #6 $150.62   10.828%   $166.9291   $166.93   $166.95   $166.90  
  Purchase #7 $207.50   3.609%   $214.9887   $214.99   $215.00   $215.00  
  7 purchase totals = $963.81       $1,048.7121   $1,048.72   $1,048.80   $1,048.70