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	$149.36	4.820%	$156.5592	$156.56	$156.55	$156.60
Purchase #2	$173.59	10.644%	$192.0669	$192.07	$192.05	$192.10
Purchase #3	$107.26	7.670%	$115.4868	$115.49	$115.50	$115.50
Purchase #4	$52.96	13.218%	$59.9603	$59.96	$59.95	$60.00
Purchase #5	$20.40	10.453%	$22.5324	$22.53	$22.55	$22.50
Purchase #6	$89.27	12.183%	$100.1458	$100.15	$100.15	$100.10
Purchase #7	$154.51	7.477%	$166.0627	$166.06	$166.05	$166.10
7 purchase totals =	$747.35		$812.8141	$812.82	$812.80	$812.90