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	$122.64	7.407%	$131.7239	$131.72	$131.70	$131.70
Purchase #2	$152.36	8.230%	$164.8992	$164.90	$164.90	$164.90
Purchase #3	$243.58	3.523%	$252.1613	$252.16	$252.15	$252.20
Purchase #4	$116.50	5.485%	$122.89	$122.89	$122.90	$122.90
Purchase #5	$58.65	4.705%	$61.4095	$61.41	$61.40	$61.40
Purchase #6	$84.98	5.353%	$89.529	$89.53	$89.55	$89.50
Purchase #7	$74.51	4.635%	$77.9635	$77.96	$77.95	$78.00
7 purchase totals =	$853.22		$900.5764	$900.57	$900.55	$900.60