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 $152.76   9.308%   $166.9789   $166.98   $167.00   $167.00  
  Purchase #2 $69.71   11.121%   $77.4624   $77.46   $77.45   $77.50  
  Purchase #3 $169.75   4.541%   $177.4583   $177.46   $177.45   $177.50  
  Purchase #4 $109.94   10.323%   $121.2891   $121.29   $121.30   $121.30  
  Purchase #5 $62.98   4.379%   $65.7379   $65.74   $65.75   $65.70  
  Purchase #6 $198.93   8.292%   $215.4253   $215.43   $215.45   $215.40  
  Purchase #7 $221.29   3.669%   $229.4091   $229.41   $229.40   $229.40  
  7 purchase totals = $985.36       $1,053.7610   $1,053.77   $1,053.80   $1,053.80