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	$203.88	13.191%	$230.7738	$230.77	$230.75	$230.80
Purchase #2	$13.57	4.832%	$14.2257	$14.23	$14.25	$14.20
Purchase #3	$114.89	7.532%	$123.5435	$123.54	$123.55	$123.50
Purchase #4	$219.53	7.198%	$235.3318	$235.33	$235.35	$235.30
Purchase #5	$119.31	13.755%	$135.7211	$135.72	$135.70	$135.70
Purchase #6	$173.80	4.370%	$181.3951	$181.40	$181.40	$181.40
Purchase #7	$171.35	11.135%	$190.4298	$190.43	$190.45	$190.40
7 purchase totals =	$1,016.33		$1,111.4208	$1,111.42	$1,111.45	$1,111.30