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	$174.50	3.187%	$180.0613	$180.06	$180.05	$180.10
Purchase #2	$247.28	3.514%	$255.9694	$255.97	$255.95	$256.00
Purchase #3	$156.90	10.506%	$173.3839	$173.38	$173.40	$173.40
Purchase #4	$64.34	12.673%	$72.4938	$72.49	$72.50	$72.50
Purchase #5	$100.76	3.350%	$104.1355	$104.14	$104.15	$104.10
Purchase #6	$36.75	5.711%	$38.8488	$38.85	$38.85	$38.80
Purchase #7	$37.89	4.291%	$39.5159	$39.52	$39.50	$39.50
7 purchase totals =	$818.42		$864.4086	$864.41	$864.40	$864.40