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 $168.53   7.421%   $181.0366   $181.04   $181.05   $181.00  
  Purchase #2 $43.95   4.370%   $45.8706   $45.87   $45.85   $45.90  
  Purchase #3 $145.26   4.396%   $151.6456   $151.65   $151.65   $151.60  
  Purchase #4 $216.72   5.810%   $229.3114   $229.31   $229.30   $229.30  
  Purchase #5 $205.54   3.603%   $212.9456   $212.95   $212.95   $212.90  
  Purchase #6 $228.41   3.856%   $237.2175   $237.22   $237.20   $237.20  
  Purchase #7 $89.48   7.486%   $96.1785   $96.18   $96.20   $96.20  
  7 purchase totals = $1,097.89       $1,154.2058   $1,154.22   $1,154.20   $1,154.10