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 $68.71   8.655%   $74.6569   $74.66   $74.65   $74.70  
  Purchase #2 $57.72   9.740%   $63.3419   $63.34   $63.35   $63.30  
  Purchase #3 $244.85   4.530%   $255.9417   $255.94   $255.95   $255.90  
  Purchase #4 $220.98   11.502%   $246.3971   $246.40   $246.40   $246.40  
  Purchase #5 $172.74   13.274%   $195.6695   $195.67   $195.65   $195.70  
  Purchase #6 $195.83   8.873%   $213.206   $213.21   $213.20   $213.20  
  Purchase #7 $61.73   8.752%   $67.1326   $67.13   $67.15   $67.10  
  7 purchase totals = $1,022.56       $1,116.3457   $1,116.35   $1,116.35   $1,116.30