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	$27.65	6.621%	$29.4807	$29.48	$29.50	$29.50
Purchase #2	$18.89	7.590%	$20.3238	$20.32	$20.30	$20.30
Purchase #3	$35.32	3.288%	$36.4813	$36.48	$36.50	$36.50
Purchase #4	$150.69	10.114%	$165.9308	$165.93	$165.95	$165.90
Purchase #5	$94.92	5.550%	$100.1881	$100.19	$100.20	$100.20
Purchase #6	$250.76	4.177%	$261.2342	$261.23	$261.25	$261.20
Purchase #7	$117.41	5.665%	$124.0613	$124.06	$124.05	$124.10
7 purchase totals =	$695.64		$737.7002	$737.69	$737.75	$737.70