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	$117.94	7.848%	$127.1959	$127.20	$127.20	$127.20
Purchase #2	$98.58	6.700%	$105.1849	$105.18	$105.20	$105.20
Purchase #3	$204.56	8.737%	$222.4324	$222.43	$222.45	$222.40
Purchase #4	$149.82	6.430%	$159.4534	$159.45	$159.45	$159.50
Purchase #5	$39.92	5.287%	$42.0306	$42.03	$42.05	$42.00
Purchase #6	$214.43	6.754%	$228.9126	$228.91	$228.90	$228.90
Purchase #7	$30.93	3.715%	$32.079	$32.08	$32.10	$32.10
7 purchase totals =	$856.18		$917.2888	$917.28	$917.35	$917.30