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 $237.44   4.847%   $248.9487   $248.95   $248.95   $248.90  
  Purchase #2 $70.29   8.404%   $76.1972   $76.20   $76.20   $76.20  
  Purchase #3 $29.52   13.780%   $33.5879   $33.59   $33.60   $33.60  
  Purchase #4 $203.86   13.608%   $231.6013   $231.60   $231.60   $231.60  
  Purchase #5 $150.73   6.355%   $160.3089   $160.31   $160.30   $160.30  
  Purchase #6 $196.47   6.777%   $209.7848   $209.78   $209.80   $209.80  
  Purchase #7 $166.80   10.532%   $184.3674   $184.37   $184.35   $184.40  
  7 purchase totals = $1,055.11       $1,144.7962   $1,144.80   $1,144.80   $1,144.80