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	$61.83	8.162%	$66.8766	$66.88	$66.90	$66.90
Purchase #2	$22.73	7.316%	$24.3929	$24.39	$24.40	$24.40
Purchase #3	$103.27	5.801%	$109.2607	$109.26	$109.25	$109.30
Purchase #4	$56.82	10.199%	$62.6151	$62.62	$62.60	$62.60
Purchase #5	$82.75	7.367%	$88.8462	$88.85	$88.85	$88.80
Purchase #6	$149.25	12.605%	$168.063	$168.06	$168.05	$168.10
Purchase #7	$37.61	8.181%	$40.6869	$40.69	$40.70	$40.70
7 purchase totals =	$514.26		$560.7414	$560.75	$560.75	$560.80