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	$194.65	7.703%	$209.6439	$209.64	$209.65	$209.60
Purchase #2	$114.34	11.677%	$127.6915	$127.69	$127.70	$127.70
Purchase #3	$25.40	8.626%	$27.591	$27.59	$27.60	$27.60
Purchase #4	$104.75	6.192%	$111.2361	$111.24	$111.25	$111.20
Purchase #5	$5.57	9.620%	$6.1058	$6.11	$6.10	$6.10
Purchase #6	$165.88	13.659%	$188.5375	$188.54	$188.55	$188.50
Purchase #7	$71.45	8.412%	$77.4604	$77.46	$77.45	$77.50
7 purchase totals =	$682.04		$748.2662	$748.27	$748.30	$748.20