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	$194.40	9.281%	$212.4423	$212.44	$212.45	$212.40
Purchase #2	$17.69	3.534%	$18.3152	$18.32	$18.30	$18.30
Purchase #3	$98.74	13.304%	$111.8764	$111.88	$111.90	$111.90
Purchase #4	$36.95	9.434%	$40.4359	$40.44	$40.45	$40.40
Purchase #5	$117.26	7.852%	$126.4673	$126.47	$126.45	$126.50
Purchase #6	$141.93	7.786%	$152.9807	$152.98	$153.00	$153.00
Purchase #7	$59.66	12.820%	$67.3084	$67.31	$67.30	$67.30
7 purchase totals =	$666.63		$729.8262	$729.84	$729.85	$729.80