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	$39.83	8.673%	$43.2845	$43.28	$43.30	$43.30
Purchase #2	$110.79	12.312%	$124.4305	$124.43	$124.45	$124.40
Purchase #3	$123.48	5.321%	$130.0504	$130.05	$130.05	$130.10
Purchase #4	$231.42	5.529%	$244.2152	$244.22	$244.20	$244.20
Purchase #5	$92.30	11.607%	$103.0133	$103.01	$103.00	$103.00
Purchase #6	$26.69	6.578%	$28.4457	$28.45	$28.45	$28.40
Purchase #7	$95.36	4.550%	$99.6989	$99.70	$99.70	$99.70
7 purchase totals =	$719.87		$773.1385	$773.14	$773.15	$773.10