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	$233.32	6.425%	$248.3108	$248.31	$248.30	$248.30
Purchase #2	$9.52	11.636%	$10.6277	$10.63	$10.65	$10.60
Purchase #3	$99.49	6.654%	$106.1101	$106.11	$106.10	$106.10
Purchase #4	$19.66	10.328%	$21.6905	$21.69	$21.70	$21.70
Purchase #5	$210.28	10.465%	$232.2858	$232.29	$232.30	$232.30
Purchase #6	$31.38	3.433%	$32.4573	$32.46	$32.45	$32.50
Purchase #7	$55.71	6.390%	$59.2699	$59.27	$59.25	$59.30
7 purchase totals =	$659.36		$710.7521	$710.76	$710.75	$710.80