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	$200.38	9.312%	$219.0394	$219.04	$219.05	$219.00
Purchase #2	$55.59	9.448%	$60.8421	$60.84	$60.85	$60.80
Purchase #3	$235.76	8.293%	$255.3116	$255.31	$255.30	$255.30
Purchase #4	$88.99	11.833%	$99.5202	$99.52	$99.50	$99.50
Purchase #5	$96.69	4.613%	$101.1503	$101.15	$101.15	$101.20
Purchase #6	$152.48	7.838%	$164.4314	$164.43	$164.45	$164.40
Purchase #7	$52.43	10.346%	$57.8544	$57.85	$57.85	$57.90
7 purchase totals =	$882.32		$958.1494	$958.14	$958.15	$958.10