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 $215.50   10.753%   $238.6727   $238.67   $238.65   $238.70  
  Purchase #2 $154.73   3.148%   $159.6009   $159.60   $159.60   $159.60  
  Purchase #3 $150.33   7.452%   $161.5326   $161.53   $161.55   $161.50  
  Purchase #4 $124.86   3.740%   $129.5298   $129.53   $129.55   $129.50  
  Purchase #5 $127.65   5.289%   $134.4014   $134.40   $134.40   $134.40  
  Purchase #6 $24.56   8.209%   $26.5761   $26.58   $26.60   $26.60  
  Purchase #7 $216.48   3.322%   $223.6715   $223.67   $223.65   $223.70  
  7 purchase totals = $1,014.11       $1,073.9850   $1,073.98   $1,074.00   $1,074.00