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 $33.35   3.810%   $34.6206   $34.62   $34.60   $34.60  
  Purchase #2 $150.66   7.755%   $162.3437   $162.34   $162.35   $162.30  
  Purchase #3 $216.80   13.449%   $245.9574   $245.96   $245.95   $246.00  
  Purchase #4 $221.26   9.741%   $242.8129   $242.81   $242.80   $242.80  
  Purchase #5 $157.71   9.516%   $172.7177   $172.72   $172.70   $172.70  
  Purchase #6 $127.84   3.569%   $132.4026   $132.40   $132.40   $132.40  
  Purchase #7 $126.62   5.133%   $133.1194   $133.12   $133.10   $133.10  
  7 purchase totals = $1,034.24       $1,123.9743   $1,123.97   $1,123.90   $1,123.90