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	$103.92	10.626%	$114.9625	$114.96	$114.95	$115.00
Purchase #2	$123.48	13.137%	$139.7016	$139.70	$139.70	$139.70
Purchase #3	$48.54	11.581%	$54.1614	$54.16	$54.15	$54.20
Purchase #4	$49.92	4.433%	$52.133	$52.13	$52.15	$52.10
Purchase #5	$250.58	6.139%	$265.9631	$265.96	$265.95	$266.00
Purchase #6	$78.87	10.192%	$86.9084	$86.91	$86.90	$86.90
Purchase #7	$45.44	11.146%	$50.5047	$50.50	$50.50	$50.50
7 purchase totals =	$700.75		$764.3347	$764.32	$764.30	$764.40