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	$42.32	10.132%	$46.6079	$46.61	$46.60	$46.60
Purchase #2	$83.78	9.453%	$91.6997	$91.70	$91.70	$91.70
Purchase #3	$173.30	10.658%	$191.7703	$191.77	$191.75	$191.80
Purchase #4	$145.28	5.743%	$153.6234	$153.62	$153.60	$153.60
Purchase #5	$137.69	12.333%	$154.6713	$154.67	$154.65	$154.70
Purchase #6	$152.52	12.813%	$172.0624	$172.06	$172.05	$172.10
Purchase #7	$75.98	5.590%	$80.2273	$80.23	$80.25	$80.20
7 purchase totals =	$810.87		$890.6623	$890.66	$890.60	$890.70