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	$153.73	7.240%	$164.8601	$164.86	$164.85	$164.90
Purchase #2	$164.67	4.482%	$172.0505	$172.05	$172.05	$172.10
Purchase #3	$48.94	10.367%	$54.0136	$54.01	$54.00	$54.00
Purchase #4	$109.90	9.667%	$120.524	$120.52	$120.50	$120.50
Purchase #5	$15.45	8.383%	$16.7452	$16.75	$16.75	$16.70
Purchase #6	$144.27	10.736%	$159.7588	$159.76	$159.75	$159.80
Purchase #7	$157.49	6.615%	$167.908	$167.91	$167.90	$167.90
7 purchase totals =	$794.45		$855.8602	$855.86	$855.80	$855.90