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	$213.52	13.113%	$241.5189	$241.52	$241.50	$241.50
Purchase #2	$230.79	6.533%	$245.8675	$245.87	$245.85	$245.90
Purchase #3	$62.29	8.313%	$67.4682	$67.47	$67.45	$67.50
Purchase #4	$205.44	10.253%	$226.5038	$226.50	$226.50	$226.50
Purchase #5	$209.58	3.778%	$217.4979	$217.50	$217.50	$217.50
Purchase #6	$31.78	11.526%	$35.443	$35.44	$35.45	$35.40
Purchase #7	$180.85	8.485%	$196.1951	$196.20	$196.20	$196.20
7 purchase totals =	$1,134.25		$1,230.4944	$1,230.50	$1,230.45	$1,230.50