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 $57.96   5.763%   $61.3002   $61.30   $61.30   $61.30  
  Purchase #2 $118.67   5.822%   $125.579   $125.58   $125.60   $125.60  
  Purchase #3 $68.52   7.263%   $73.4966   $73.50   $73.50   $73.50  
  Purchase #4 $219.29   8.184%   $237.2367   $237.24   $237.25   $237.20  
  Purchase #5 $128.27   3.557%   $132.8326   $132.83   $132.85   $132.80  
  Purchase #6 $170.97   9.321%   $186.9061   $186.91   $186.90   $186.90  
  Purchase #7 $165.31   5.693%   $174.7211   $174.72   $174.70   $174.70  
  7 purchase totals = $928.99       $992.0723   $992.08   $992.10   $992.00