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 $67.76   6.784%   $72.3568   $72.36   $72.35   $72.40  
  Purchase #2 $216.77   7.801%   $233.6802   $233.68   $233.70   $233.70  
  Purchase #3 $169.31   12.576%   $190.6024   $190.60   $190.60   $190.60  
  Purchase #4 $102.88   4.713%   $107.7287   $107.73   $107.75   $107.70  
  Purchase #5 $55.88   8.153%   $60.4359   $60.44   $60.45   $60.40  
  Purchase #6 $225.75   4.435%   $235.762   $235.76   $235.75   $235.80  
  Purchase #7 $102.71   3.370%   $106.1713   $106.17   $106.15   $106.20  
  7 purchase totals = $941.06       $1,006.7373   $1,006.74   $1,006.75   $1,006.80