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	$145.51	5.116%	$152.9543	$152.95	$152.95	$153.00
Purchase #2	$229.74	5.123%	$241.5096	$241.51	$241.50	$241.50
Purchase #3	$56.85	5.380%	$59.9085	$59.91	$59.90	$59.90
Purchase #4	$161.52	13.496%	$183.3187	$183.32	$183.30	$183.30
Purchase #5	$144.79	10.547%	$160.061	$160.06	$160.05	$160.10
Purchase #6	$130.86	11.768%	$146.2596	$146.26	$146.25	$146.30
Purchase #7	$137.77	7.280%	$147.7997	$147.80	$147.80	$147.80
7 purchase totals =	$1,007.04		$1,091.8114	$1,091.81	$1,091.75	$1,091.90