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 $71.52   6.527%   $76.1881   $76.19   $76.20   $76.20  
  Purchase #2 $248.58   7.802%   $267.9742   $267.97   $267.95   $268.00  
  Purchase #3 $204.68   3.234%   $211.2994   $211.30   $211.30   $211.30  
  Purchase #4 $232.96   10.557%   $257.5536   $257.55   $257.55   $257.60  
  Purchase #5 $103.78   3.126%   $107.0242   $107.02   $107.00   $107.00  
  Purchase #6 $167.77   3.503%   $173.647   $173.65   $173.65   $173.60  
  Purchase #7 $81.50   12.872%   $91.9907   $91.99   $92.00   $92.00  
  7 purchase totals = $1,110.79       $1,185.6772   $1,185.67   $1,185.65   $1,185.70