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	$240.63	9.492%	$263.4706	$263.47	$263.45	$263.50
Purchase #2	$233.75	12.614%	$263.2352	$263.24	$263.25	$263.20
Purchase #3	$121.66	4.801%	$127.5009	$127.50	$127.50	$127.50
Purchase #4	$50.33	11.653%	$56.195	$56.20	$56.20	$56.20
Purchase #5	$106.48	4.358%	$111.1204	$111.12	$111.10	$111.10
Purchase #6	$176.40	7.498%	$189.6265	$189.63	$189.65	$189.60
Purchase #7	$55.52	11.533%	$61.9231	$61.92	$61.90	$61.90
7 purchase totals =	$984.77		$1,073.0717	$1,073.08	$1,073.05	$1,073.00