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 $169.33   3.204%   $174.7553   $174.76   $174.75   $174.80  
  Purchase #2 $190.71   7.506%   $205.0247   $205.02   $205.00   $205.00  
  Purchase #3 $139.89   3.801%   $145.2072   $145.21   $145.20   $145.20  
  Purchase #4 $55.45   11.753%   $61.967   $61.97   $61.95   $62.00  
  Purchase #5 $151.48   10.322%   $167.1158   $167.12   $167.10   $167.10  
  Purchase #6 $129.66   3.578%   $134.2992   $134.30   $134.30   $134.30  
  Purchase #7 $118.99   6.384%   $126.5863   $126.59   $126.60   $126.60  
  7 purchase totals = $955.51       $1,014.9555   $1,014.97   $1,014.90   $1,015.00