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	$242.38	11.384%	$269.9725	$269.97	$269.95	$270.00
Purchase #2	$220.43	10.125%	$242.7485	$242.75	$242.75	$242.70
Purchase #3	$247.86	12.710%	$279.363	$279.36	$279.35	$279.40
Purchase #4	$13.83	9.222%	$15.1054	$15.11	$15.10	$15.10
Purchase #5	$55.76	10.578%	$61.6583	$61.66	$61.65	$61.70
Purchase #6	$112.50	13.157%	$127.3016	$127.30	$127.30	$127.30
Purchase #7	$86.42	3.757%	$89.6668	$89.67	$89.65	$89.70
7 purchase totals =	$979.18		$1,085.8161	$1,085.82	$1,085.75	$1,085.90