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 $84.49   12.573%   $95.1129   $95.11   $95.10   $95.10  
  Purchase #2 $32.51   3.873%   $33.7691   $33.77   $33.75   $33.80  
  Purchase #3 $221.26   5.285%   $232.9536   $232.95   $232.95   $233.00  
  Purchase #4 $62.95   9.204%   $68.7439   $68.74   $68.75   $68.70  
  Purchase #5 $196.52   3.287%   $202.9796   $202.98   $203.00   $203.00  
  Purchase #6 $228.50   4.831%   $239.5388   $239.54   $239.55   $239.50  
  Purchase #7 $156.85   4.854%   $164.4635   $164.46   $164.45   $164.50  
  7 purchase totals = $983.08       $1,037.5614   $1,037.55   $1,037.55   $1,037.60