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 $61.74   3.382%   $63.828   $63.83   $63.85   $63.80  
  Purchase #2 $126.39   4.667%   $132.2886   $132.29   $132.30   $132.30  
  Purchase #3 $179.51   12.728%   $202.358   $202.36   $202.35   $202.40  
  Purchase #4 $68.34   10.217%   $75.3223   $75.32   $75.30   $75.30  
  Purchase #5 $160.28   9.532%   $175.5579   $175.56   $175.55   $175.60  
  Purchase #6 $174.64   4.867%   $183.1397   $183.14   $183.15   $183.10  
  Purchase #7 $183.28   7.492%   $197.0113   $197.01   $197.00   $197.00  
  7 purchase totals = $954.18       $1,029.5058   $1,029.51   $1,029.50   $1,029.50