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	$76.58	10.334%	$84.4938	$84.49	$84.50	$84.50
Purchase #2	$53.95	7.672%	$58.089	$58.09	$58.10	$58.10
Purchase #3	$83.67	7.243%	$89.7302	$89.73	$89.75	$89.70
Purchase #4	$103.82	5.438%	$109.4657	$109.47	$109.45	$109.50
Purchase #5	$55.26	8.153%	$59.7653	$59.77	$59.75	$59.80
Purchase #6	$50.54	12.297%	$56.7549	$56.75	$56.75	$56.80
Purchase #7	$9.81	4.700%	$10.2711	$10.27	$10.25	$10.30
7 purchase totals =	$433.63		$468.5700	$468.57	$468.55	$468.70