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 $87.37   10.627%   $96.6548   $96.65   $96.65   $96.70  
  Purchase #2 $178.99   6.442%   $190.5205   $190.52   $190.50   $190.50  
  Purchase #3 $56.26   6.716%   $60.0384   $60.04   $60.05   $60.00  
  Purchase #4 $197.73   6.409%   $210.4025   $210.40   $210.40   $210.40  
  Purchase #5 $87.85   4.487%   $91.7918   $91.79   $91.80   $91.80  
  Purchase #6 $49.87   7.422%   $53.5714   $53.57   $53.55   $53.60  
  Purchase #7 $55.84   5.513%   $58.9185   $58.92   $58.90   $58.90  
  7 purchase totals = $713.91       $761.8979   $761.89   $761.85   $761.90