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	$65.61	8.452%	$71.1554	$71.16	$71.15	$71.20
Purchase #2	$37.64	5.427%	$39.6827	$39.68	$39.70	$39.70
Purchase #3	$151.69	12.286%	$170.3266	$170.33	$170.35	$170.30
Purchase #4	$92.33	4.346%	$96.3427	$96.34	$96.35	$96.30
Purchase #5	$90.67	5.142%	$95.3323	$95.33	$95.35	$95.30
Purchase #6	$93.98	7.228%	$100.7729	$100.77	$100.75	$100.80
Purchase #7	$159.76	5.581%	$168.6762	$168.68	$168.70	$168.70
7 purchase totals =	$691.68		$742.2888	$742.29	$742.35	$742.30