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 $148.39   9.580%   $162.6058   $162.61   $162.60   $162.60  
  Purchase #2 $28.93   10.561%   $31.9853   $31.99   $32.00   $32.00  
  Purchase #3 $244.74   9.336%   $267.5889   $267.59   $267.60   $267.60  
  Purchase #4 $43.26   4.181%   $45.0687   $45.07   $45.05   $45.10  
  Purchase #5 $113.27   3.569%   $117.3126   $117.31   $117.30   $117.30  
  Purchase #6 $142.58   7.371%   $153.0896   $153.09   $153.10   $153.10  
  Purchase #7 $214.78   4.814%   $225.1195   $225.12   $225.10   $225.10  
  7 purchase totals = $935.95       $1,002.7704   $1,002.78   $1,002.75   $1,002.80