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	$59.79	9.518%	$65.4808	$65.48	$65.50	$65.50
Purchase #2	$77.82	6.138%	$82.5966	$82.60	$82.60	$82.60
Purchase #3	$80.72	7.680%	$86.9193	$86.92	$86.90	$86.90
Purchase #4	$130.52	4.617%	$136.5461	$136.55	$136.55	$136.50
Purchase #5	$32.55	12.295%	$36.552	$36.55	$36.55	$36.60
Purchase #6	$45.71	5.628%	$48.2826	$48.28	$48.30	$48.30
Purchase #7	$18.75	5.232%	$19.731	$19.73	$19.75	$19.70
7 purchase totals =	$445.86		$476.1084	$476.11	$476.15	$476.10