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 $117.68   7.713%   $126.7567   $126.76   $126.75   $126.80  
  Purchase #2 $233.87   13.551%   $265.5617   $265.56   $265.55   $265.60  
  Purchase #3 $88.49   8.351%   $95.8798   $95.88   $95.90   $95.90  
  Purchase #4 $160.51   9.348%   $175.5145   $175.51   $175.50   $175.50  
  Purchase #5 $110.63   11.818%   $123.7043   $123.70   $123.70   $123.70  
  Purchase #6 $88.57   8.525%   $96.1206   $96.12   $96.10   $96.10  
  Purchase #7 $159.34   8.323%   $172.6019   $172.60   $172.60   $172.60  
  7 purchase totals = $959.09       $1,056.1395   $1,056.13   $1,056.10   $1,056.20