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	$175.90	5.202%	$185.0503	$185.05	$185.05	$185.10
Purchase #2	$53.73	7.289%	$57.6464	$57.65	$57.65	$57.60
Purchase #3	$73.78	13.789%	$83.9535	$83.95	$83.95	$84.00
Purchase #4	$20.84	3.323%	$21.5325	$21.53	$21.55	$21.50
Purchase #5	$200.71	13.489%	$227.7838	$227.78	$227.80	$227.80
Purchase #6	$49.67	11.634%	$55.4486	$55.45	$55.45	$55.40
Purchase #7	$91.77	7.108%	$98.293	$98.29	$98.30	$98.30
7 purchase totals =	$666.40		$729.7081	$729.70	$729.75	$729.70