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	$14.49	5.401%	$15.2726	$15.27	$15.25	$15.30
Purchase #2	$250.92	10.743%	$277.8763	$277.88	$277.90	$277.90
Purchase #3	$69.77	4.477%	$72.8936	$72.89	$72.90	$72.90
Purchase #4	$147.32	8.296%	$159.5417	$159.54	$159.55	$159.50
Purchase #5	$63.70	13.226%	$72.125	$72.13	$72.15	$72.10
Purchase #6	$91.29	5.602%	$96.4041	$96.40	$96.40	$96.40
Purchase #7	$43.99	3.709%	$45.6216	$45.62	$45.60	$45.60
7 purchase totals =	$681.48		$739.7349	$739.73	$739.75	$739.70