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	$185.77	4.836%	$194.7538	$194.75	$194.75	$194.80
Purchase #2	$200.50	11.149%	$222.8537	$222.85	$222.85	$222.90
Purchase #3	$155.28	5.676%	$164.0937	$164.09	$164.10	$164.10
Purchase #4	$99.90	7.184%	$107.0768	$107.08	$107.10	$107.10
Purchase #5	$68.53	7.178%	$73.4491	$73.45	$73.45	$73.40
Purchase #6	$166.37	13.640%	$189.0629	$189.06	$189.05	$189.10
Purchase #7	$164.71	4.459%	$172.0544	$172.05	$172.05	$172.10
7 purchase totals =	$1,041.06		$1,123.3444	$1,123.33	$1,123.35	$1,123.50