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	$165.31	12.179%	$185.4431	$185.44	$185.45	$185.40
Purchase #2	$176.90	4.721%	$185.2514	$185.25	$185.25	$185.30
Purchase #3	$228.93	11.399%	$255.0257	$255.03	$255.05	$255.00
Purchase #4	$42.69	9.869%	$46.9031	$46.90	$46.90	$46.90
Purchase #5	$48.84	9.311%	$53.3875	$53.39	$53.40	$53.40
Purchase #6	$20.99	12.483%	$23.6102	$23.61	$23.60	$23.60
Purchase #7	$175.41	9.327%	$191.7705	$191.77	$191.75	$191.80
7 purchase totals =	$859.07		$941.3915	$941.39	$941.40	$941.40