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	$148.95	6.545%	$158.6988	$158.70	$158.70	$158.70
Purchase #2	$26.52	9.688%	$29.0893	$29.09	$29.10	$29.10
Purchase #3	$140.82	5.314%	$148.3032	$148.30	$148.30	$148.30
Purchase #4	$47.26	13.281%	$53.5366	$53.54	$53.55	$53.50
Purchase #5	$35.68	5.478%	$37.6346	$37.63	$37.65	$37.60
Purchase #6	$108.45	13.692%	$123.299	$123.30	$123.30	$123.30
Purchase #7	$163.95	13.180%	$185.5586	$185.56	$185.55	$185.60
7 purchase totals =	$671.63		$736.1201	$736.12	$736.15	$736.10