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 $184.79   5.861%   $195.6205   $195.62   $195.60   $195.60  
  Purchase #2 $184.63   11.502%   $205.8661   $205.87   $205.85   $205.90  
  Purchase #3 $171.42   9.847%   $188.2997   $188.30   $188.30   $188.30  
  Purchase #4 $160.94   10.776%   $178.2829   $178.28   $178.30   $178.30  
  Purchase #5 $87.95   9.870%   $96.6307   $96.63   $96.65   $96.60  
  Purchase #6 $129.26   3.337%   $133.5734   $133.57   $133.55   $133.60  
  Purchase #7 $42.70   4.844%   $44.7684   $44.77   $44.75   $44.80  
  7 purchase totals = $961.69       $1,043.0417   $1,043.04   $1,043.00   $1,043.10