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	$105.59	8.222%	$114.2716	$114.27	$114.25	$114.30
Purchase #2	$76.98	13.764%	$87.5755	$87.58	$87.60	$87.60
Purchase #3	$31.76	5.227%	$33.4201	$33.42	$33.40	$33.40
Purchase #4	$19.52	3.205%	$20.1456	$20.15	$20.15	$20.10
Purchase #5	$235.29	7.616%	$253.2097	$253.21	$253.20	$253.20
Purchase #6	$137.52	4.207%	$143.3055	$143.31	$143.30	$143.30
Purchase #7	$215.58	4.629%	$225.5592	$225.56	$225.55	$225.60
7 purchase totals =	$822.24		$877.4872	$877.50	$877.45	$877.50