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	$151.64	9.683%	$166.3233	$166.32	$166.30	$166.30
Purchase #2	$77.27	10.458%	$85.3509	$85.35	$85.35	$85.40
Purchase #3	$92.38	6.409%	$98.3006	$98.30	$98.30	$98.30
Purchase #4	$134.92	8.437%	$146.3032	$146.30	$146.30	$146.30
Purchase #5	$83.52	9.102%	$91.122	$91.12	$91.10	$91.10
Purchase #6	$145.70	7.163%	$156.1365	$156.14	$156.15	$156.10
Purchase #7	$46.89	3.579%	$48.5682	$48.57	$48.55	$48.60
7 purchase totals =	$732.32		$792.1047	$792.10	$792.05	$792.10