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	$111.99	5.690%	$118.3622	$118.36	$118.35	$118.40
Purchase #2	$236.50	7.796%	$254.9375	$254.94	$254.95	$254.90
Purchase #3	$241.45	5.651%	$255.0943	$255.09	$255.10	$255.10
Purchase #4	$50.61	3.267%	$52.2634	$52.26	$52.25	$52.30
Purchase #5	$159.77	7.713%	$172.0931	$172.09	$172.10	$172.10
Purchase #6	$210.97	5.368%	$222.2949	$222.29	$222.30	$222.30
Purchase #7	$187.98	6.410%	$200.0295	$200.03	$200.05	$200.00
7 purchase totals =	$1,199.27		$1,275.0749	$1,275.06	$1,275.10	$1,275.10