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	$166.64	7.230%	$178.6881	$178.69	$178.70	$178.70
Purchase #2	$72.89	5.277%	$76.7364	$76.74	$76.75	$76.70
Purchase #3	$68.74	4.389%	$71.757	$71.76	$71.75	$71.80
Purchase #4	$101.58	9.473%	$111.2027	$111.20	$111.20	$111.20
Purchase #5	$152.61	10.188%	$168.1579	$168.16	$168.15	$168.20
Purchase #6	$86.68	10.559%	$95.8325	$95.83	$95.85	$95.80
Purchase #7	$72.73	10.610%	$80.4467	$80.45	$80.45	$80.40
7 purchase totals =	$721.87		$782.8213	$782.83	$782.85	$782.80