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 $195.90   9.739%   $214.9787   $214.98   $215.00   $215.00  
  Purchase #2 $137.63   11.244%   $153.1051   $153.11   $153.10   $153.10  
  Purchase #3 $124.87   7.668%   $134.445   $134.45   $134.45   $134.40  
  Purchase #4 $52.65   9.850%   $57.836   $57.84   $57.85   $57.80  
  Purchase #5 $182.91   4.416%   $190.9873   $190.99   $191.00   $191.00  
  Purchase #6 $142.26   6.844%   $151.9963   $152.00   $152.00   $152.00  
  Purchase #7 $156.53   8.844%   $170.3735   $170.37   $170.35   $170.40  
  7 purchase totals = $992.75       $1,073.7219   $1,073.74   $1,073.75   $1,073.70