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 $85.57   12.775%   $96.5016   $96.50   $96.50   $96.50  
  Purchase #2 $208.32   12.231%   $233.7996   $233.80   $233.80   $233.80  
  Purchase #3 $25.74   7.647%   $27.7083   $27.71   $27.70   $27.70  
  Purchase #4 $60.60   5.673%   $64.0378   $64.04   $64.05   $64.00  
  Purchase #5 $145.51   9.254%   $158.9755   $158.98   $159.00   $159.00  
  Purchase #6 $202.28   6.285%   $214.9933   $214.99   $215.00   $215.00  
  Purchase #7 $225.27   7.178%   $241.4399   $241.44   $241.45   $241.40  
  7 purchase totals = $953.29       $1,037.4560   $1,037.46   $1,037.50   $1,037.40