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 $197.88   5.653%   $209.0662   $209.07   $209.05   $209.10  
  Purchase #2 $62.97   5.658%   $66.5328   $66.53   $66.55   $66.50  
  Purchase #3 $171.76   12.534%   $193.2884   $193.29   $193.30   $193.30  
  Purchase #4 $237.88   12.350%   $267.2582   $267.26   $267.25   $267.30  
  Purchase #5 $202.84   13.864%   $230.9617   $230.96   $230.95   $231.00  
  Purchase #6 $167.87   4.638%   $175.6558   $175.66   $175.65   $175.70  
  Purchase #7 $60.70   12.532%   $68.3069   $68.31   $68.30   $68.30  
  7 purchase totals = $1,101.90       $1,211.0700   $1,211.08   $1,211.05   $1,211.20