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 $201.30   4.486%   $210.3303   $210.33   $210.35   $210.30  
  Purchase #2 $147.72   4.737%   $154.7175   $154.72   $154.70   $154.70  
  Purchase #3 $241.68   13.121%   $273.3908   $273.39   $273.40   $273.40  
  Purchase #4 $233.82   13.563%   $265.533   $265.53   $265.55   $265.50  
  Purchase #5 $224.99   8.659%   $244.4719   $244.47   $244.45   $244.50  
  Purchase #6 $212.99   6.415%   $226.6533   $226.65   $226.65   $226.70  
  Purchase #7 $223.51   6.277%   $237.5397   $237.54   $237.55   $237.50  
  7 purchase totals = $1,486.01       $1,612.6365   $1,612.63   $1,612.65   $1,612.60