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	$33.51	12.341%	$37.6455	$37.65	$37.65	$37.60
Purchase #2	$100.58	13.525%	$114.1834	$114.18	$114.20	$114.20
Purchase #3	$38.87	12.485%	$43.7229	$43.72	$43.70	$43.70
Purchase #4	$116.50	12.479%	$131.038	$131.04	$131.05	$131.00
Purchase #5	$96.81	7.275%	$103.8529	$103.85	$103.85	$103.90
Purchase #6	$106.76	7.305%	$114.5588	$114.56	$114.55	$114.60
Purchase #7	$162.82	10.720%	$180.2743	$180.27	$180.25	$180.30
7 purchase totals =	$655.85		$725.2758	$725.27	$725.25	$725.30