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	$118.50	5.103%	$124.5471	$124.55	$124.55	$124.50
Purchase #2	$121.98	7.204%	$130.7674	$130.77	$130.75	$130.80
Purchase #3	$30.56	8.788%	$33.2456	$33.25	$33.25	$33.20
Purchase #4	$58.32	7.120%	$62.4724	$62.47	$62.45	$62.50
Purchase #5	$116.66	8.433%	$126.4979	$126.50	$126.50	$126.50
Purchase #6	$48.85	12.636%	$55.0227	$55.02	$55.00	$55.00
Purchase #7	$101.38	13.262%	$114.825	$114.83	$114.85	$114.80
7 purchase totals =	$596.25		$647.3781	$647.39	$647.35	$647.30