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 $108.41   4.820%   $113.6354   $113.64   $113.65   $113.60  
  Purchase #2 $213.26   9.460%   $233.4344   $233.43   $233.45   $233.40  
  Purchase #3 $158.61   7.807%   $170.9927   $170.99   $171.00   $171.00  
  Purchase #4 $167.96   3.127%   $173.2121   $173.21   $173.20   $173.20  
  Purchase #5 $134.32   11.197%   $149.3598   $149.36   $149.35   $149.40  
  Purchase #6 $95.75   6.666%   $102.1327   $102.13   $102.15   $102.10  
  Purchase #7 $61.33   5.216%   $64.529   $64.53   $64.55   $64.50  
  7 purchase totals = $939.64       $1,007.2961   $1,007.29   $1,007.35   $1,007.20