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 $42.50   8.538%   $46.1287   $46.13   $46.15   $46.10  
  Purchase #2 $226.94   6.787%   $242.3424   $242.34   $242.35   $242.30  
  Purchase #3 $191.70   7.723%   $206.505   $206.51   $206.50   $206.50  
  Purchase #4 $19.59   8.677%   $21.2898   $21.29   $21.30   $21.30  
  Purchase #5 $219.45   3.191%   $226.4526   $226.45   $226.45   $226.50  
  Purchase #6 $210.75   4.550%   $220.3391   $220.34   $220.35   $220.30  
  Purchase #7 $124.97   5.625%   $131.9996   $132.00   $132.00   $132.00  
  7 purchase totals = $1,035.90       $1,095.0572   $1,095.06   $1,095.10   $1,095.00