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 $192.81   4.411%   $201.3148   $201.31   $201.30   $201.30  
  Purchase #2 $237.31   10.506%   $262.2418   $262.24   $262.25   $262.20  
  Purchase #3 $65.82   6.644%   $70.1931   $70.19   $70.20   $70.20  
  Purchase #4 $61.30   8.393%   $66.4449   $66.44   $66.45   $66.40  
  Purchase #5 $160.51   7.230%   $172.1149   $172.11   $172.10   $172.10  
  Purchase #6 $64.45   4.818%   $67.5552   $67.56   $67.55   $67.60  
  Purchase #7 $61.26   9.546%   $67.1079   $67.11   $67.10   $67.10  
  7 purchase totals = $843.46       $906.9726   $906.96   $906.95   $906.90