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 $66.26   13.114%   $74.9493   $74.95   $74.95   $74.90  
  Purchase #2 $152.77   8.446%   $165.673   $165.67   $165.65   $165.70  
  Purchase #3 $105.64   11.658%   $117.9555   $117.96   $117.95   $118.00  
  Purchase #4 $159.74   11.595%   $178.2619   $178.26   $178.25   $178.30  
  Purchase #5 $143.42   13.154%   $162.2855   $162.29   $162.30   $162.30  
  Purchase #6 $204.48   5.380%   $215.481   $215.48   $215.50   $215.50  
  Purchase #7 $166.52   12.282%   $186.972   $186.97   $186.95   $187.00  
  7 purchase totals = $998.83       $1,101.5782   $1,101.58   $1,101.55   $1,101.70