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	$54.76	8.556%	$59.4453	$59.45	$59.45	$59.40
Purchase #2	$190.87	8.406%	$206.9145	$206.91	$206.90	$206.90
Purchase #3	$79.97	11.305%	$89.0106	$89.01	$89.00	$89.00
Purchase #4	$230.33	11.135%	$255.9772	$255.98	$256.00	$256.00
Purchase #5	$228.95	3.517%	$237.0022	$237.00	$237.00	$237.00
Purchase #6	$247.45	12.575%	$278.5668	$278.57	$278.55	$278.60
Purchase #7	$99.93	5.222%	$105.1483	$105.15	$105.15	$105.10
7 purchase totals =	$1,132.26		$1,232.0649	$1,232.07	$1,232.05	$1,232.00