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 $68.34   11.219%   $76.0071   $76.01   $76.00   $76.00  
  Purchase #2 $129.77   12.122%   $145.5007   $145.50   $145.50   $145.50  
  Purchase #3 $209.92   10.372%   $231.6929   $231.69   $231.70   $231.70  
  Purchase #4 $230.33   4.604%   $240.9344   $240.93   $240.95   $240.90  
  Purchase #5 $217.51   12.845%   $245.4492   $245.45   $245.45   $245.40  
  Purchase #6 $88.44   13.667%   $100.5271   $100.53   $100.55   $100.50  
  Purchase #7 $176.30   4.481%   $184.2   $184.20   $184.20   $184.20  
  7 purchase totals = $1,120.61       $1,224.3114   $1,224.31   $1,224.35   $1,224.20