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	$53.83	10.117%	$59.276	$59.28	$59.30	$59.30
Purchase #2	$101.57	12.144%	$113.9047	$113.90	$113.90	$113.90
Purchase #3	$58.44	3.278%	$60.3557	$60.36	$60.35	$60.40
Purchase #4	$117.68	11.613%	$131.3462	$131.35	$131.35	$131.30
Purchase #5	$148.69	11.115%	$165.2169	$165.22	$165.20	$165.20
Purchase #6	$242.81	13.119%	$274.6642	$274.66	$274.65	$274.70
Purchase #7	$70.50	7.563%	$75.8319	$75.83	$75.85	$75.80
7 purchase totals =	$793.52		$880.5956	$880.60	$880.60	$880.60