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	$28.71	9.501%	$31.4377	$31.44	$31.45	$31.40
Purchase #2	$120.50	11.622%	$134.5045	$134.50	$134.50	$134.50
Purchase #3	$225.40	12.814%	$254.2828	$254.28	$254.30	$254.30
Purchase #4	$102.86	6.310%	$109.3505	$109.35	$109.35	$109.40
Purchase #5	$172.82	10.335%	$190.6809	$190.68	$190.70	$190.70
Purchase #6	$194.40	3.650%	$201.4956	$201.50	$201.50	$201.50
Purchase #7	$158.85	9.136%	$173.3625	$173.36	$173.35	$173.40
7 purchase totals =	$1,003.54		$1,095.1145	$1,095.11	$1,095.15	$1,095.20