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	$207.78	11.252%	$231.1594	$231.16	$231.15	$231.20
Purchase #2	$39.29	7.242%	$42.1354	$42.14	$42.15	$42.10
Purchase #3	$43.47	10.327%	$47.9591	$47.96	$47.95	$48.00
Purchase #4	$173.65	6.774%	$185.4131	$185.41	$185.40	$185.40
Purchase #5	$173.53	6.259%	$184.3912	$184.39	$184.40	$184.40
Purchase #6	$250.73	7.184%	$268.7424	$268.74	$268.75	$268.70
Purchase #7	$114.72	3.274%	$118.4759	$118.48	$118.50	$118.50
7 purchase totals =	$1,003.17		$1,078.2765	$1,078.28	$1,078.30	$1,078.30