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	$183.85	11.415%	$204.8365	$204.84	$204.85	$204.80
Purchase #2	$35.55	5.359%	$37.4551	$37.46	$37.45	$37.50
Purchase #3	$187.31	12.667%	$211.0366	$211.04	$211.05	$211.00
Purchase #4	$197.53	7.178%	$211.7087	$211.71	$211.70	$211.70
Purchase #5	$77.52	5.487%	$81.7735	$81.77	$81.75	$81.80
Purchase #6	$74.85	4.293%	$78.0633	$78.06	$78.05	$78.10
Purchase #7	$92.57	13.849%	$105.39	$105.39	$105.40	$105.40
7 purchase totals =	$849.18		$930.2637	$930.27	$930.25	$930.30