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 $87.96   9.834%   $96.61   $96.61   $96.60   $96.60  
  Purchase #2 $95.33   8.202%   $103.149   $103.15   $103.15   $103.10  
  Purchase #3 $245.65   9.842%   $269.8269   $269.83   $269.85   $269.80  
  Purchase #4 $39.54   12.333%   $44.4165   $44.42   $44.40   $44.40  
  Purchase #5 $119.89   4.426%   $125.1963   $125.20   $125.20   $125.20  
  Purchase #6 $194.55   12.824%   $219.4991   $219.50   $219.50   $219.50  
  Purchase #7 $188.92   8.210%   $204.4303   $204.43   $204.45   $204.40  
  7 purchase totals = $971.84       $1,063.1281   $1,063.14   $1,063.15   $1,063.00