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 $86.91   8.729%   $94.4964   $94.50   $94.50   $94.50  
  Purchase #2 $30.97   7.511%   $33.2962   $33.30   $33.30   $33.30  
  Purchase #3 $142.53   12.272%   $160.0213   $160.02   $160.00   $160.00  
  Purchase #4 $53.29   6.606%   $56.8103   $56.81   $56.80   $56.80  
  Purchase #5 $139.30   9.231%   $152.1588   $152.16   $152.15   $152.20  
  Purchase #6 $24.78   11.248%   $27.5673   $27.57   $27.55   $27.60  
  Purchase #7 $218.26   6.307%   $232.0257   $232.03   $232.05   $232.00  
  7 purchase totals = $696.04       $756.3760   $756.39   $756.35   $756.40