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 $54.81   11.513%   $61.1203   $61.12   $61.10   $61.10  
  Purchase #2 $236.26   8.232%   $255.7089   $255.71   $255.70   $255.70  
  Purchase #3 $67.27   12.372%   $75.5926   $75.59   $75.60   $75.60  
  Purchase #4 $161.60   11.313%   $179.8818   $179.88   $179.90   $179.90  
  Purchase #5 $231.83   6.252%   $246.324   $246.32   $246.30   $246.30  
  Purchase #6 $172.67   8.812%   $187.8857   $187.89   $187.90   $187.90  
  Purchase #7 $184.91   3.288%   $190.9898   $190.99   $191.00   $191.00  
  7 purchase totals = $1,109.35       $1,197.5031   $1,197.50   $1,197.50   $1,197.50