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	$248.65	10.507%	$274.7757	$274.78	$274.80	$274.80
Purchase #2	$128.42	9.404%	$140.4966	$140.50	$140.50	$140.50
Purchase #3	$29.27	13.307%	$33.165	$33.17	$33.15	$33.20
Purchase #4	$228.82	6.160%	$242.9153	$242.92	$242.90	$242.90
Purchase #5	$101.97	8.172%	$110.303	$110.30	$110.30	$110.30
Purchase #6	$143.27	4.798%	$150.1441	$150.14	$150.15	$150.10
Purchase #7	$52.30	13.381%	$59.2983	$59.30	$59.30	$59.30
7 purchase totals =	$932.70		$1,011.0980	$1,011.11	$1,011.10	$1,011.10