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	$178.35	6.807%	$190.4903	$190.49	$190.50	$190.50
Purchase #2	$95.87	4.803%	$100.4746	$100.47	$100.45	$100.50
Purchase #3	$134.98	10.819%	$149.5835	$149.58	$149.60	$149.60
Purchase #4	$21.68	5.567%	$22.8869	$22.89	$22.90	$22.90
Purchase #5	$33.97	10.687%	$37.6004	$37.60	$37.60	$37.60
Purchase #6	$142.29	3.751%	$147.6273	$147.63	$147.65	$147.60
Purchase #7	$247.56	7.797%	$266.8623	$266.86	$266.85	$266.90
7 purchase totals =	$854.70		$915.5253	$915.52	$915.55	$915.60