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 $98.66   3.370%   $101.9848   $101.98   $102.00   $102.00  
  Purchase #2 $126.96   11.343%   $141.3611   $141.36   $141.35   $141.40  
  Purchase #3 $74.56   4.337%   $77.7937   $77.79   $77.80   $77.80  
  Purchase #4 $51.35   4.400%   $53.6094   $53.61   $53.60   $53.60  
  Purchase #5 $218.48   9.633%   $239.5262   $239.53   $239.55   $239.50  
  Purchase #6 $64.48   6.397%   $68.6048   $68.60   $68.60   $68.60  
  Purchase #7 $110.59   7.648%   $119.0479   $119.05   $119.05   $119.00  
  7 purchase totals = $745.08       $801.9279   $801.92   $801.95   $801.90