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 $90.86   4.278%   $94.747   $94.75   $94.75   $94.70  
  Purchase #2 $184.69   6.667%   $197.0033   $197.00   $197.00   $197.00  
  Purchase #3 $16.40   4.489%   $17.1362   $17.14   $17.15   $17.10  
  Purchase #4 $240.46   10.736%   $266.2758   $266.28   $266.30   $266.30  
  Purchase #5 $71.56   5.344%   $75.3842   $75.38   $75.40   $75.40  
  Purchase #6 $174.44   4.607%   $182.4765   $182.48   $182.50   $182.50  
  Purchase #7 $246.79   12.573%   $277.8189   $277.82   $277.80   $277.80  
  7 purchase totals = $1,025.20       $1,110.8419   $1,110.85   $1,110.90   $1,110.80