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	$164.42	9.165%	$179.4891	$179.49	$179.50	$179.50
Purchase #2	$45.86	6.189%	$48.6983	$48.70	$48.70	$48.70
Purchase #3	$74.33	5.801%	$78.6419	$78.64	$78.65	$78.60
Purchase #4	$58.92	9.180%	$64.3289	$64.33	$64.35	$64.30
Purchase #5	$77.90	7.521%	$83.7589	$83.76	$83.75	$83.80
Purchase #6	$191.94	4.505%	$200.5869	$200.59	$200.60	$200.60
Purchase #7	$144.61	5.794%	$152.9887	$152.99	$153.00	$153.00
7 purchase totals =	$757.98		$808.4927	$808.50	$808.55	$808.50