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	$47.81	3.663%	$49.5613	$49.56	$49.55	$49.60
Purchase #2	$60.38	5.162%	$63.4968	$63.50	$63.50	$63.50
Purchase #3	$79.93	12.141%	$89.6343	$89.63	$89.65	$89.60
Purchase #4	$119.66	9.741%	$131.3161	$131.32	$131.30	$131.30
Purchase #5	$118.30	4.181%	$123.2461	$123.25	$123.25	$123.20
Purchase #6	$105.56	4.369%	$110.1719	$110.17	$110.15	$110.20
Purchase #7	$56.43	11.122%	$62.7061	$62.71	$62.70	$62.70
7 purchase totals =	$588.07		$630.1326	$630.14	$630.10	$630.10