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	$214.98	4.478%	$224.6068	$224.61	$224.60	$224.60
Purchase #2	$185.72	8.787%	$202.0392	$202.04	$202.05	$202.00
Purchase #3	$91.72	13.304%	$103.9224	$103.92	$103.90	$103.90
Purchase #4	$40.66	3.686%	$42.1587	$42.16	$42.15	$42.20
Purchase #5	$192.28	11.327%	$214.0596	$214.06	$214.05	$214.10
Purchase #6	$14.53	4.150%	$15.133	$15.13	$15.15	$15.10
Purchase #7	$18.89	7.557%	$20.3175	$20.32	$20.30	$20.30
7 purchase totals =	$758.78		$822.2372	$822.24	$822.20	$822.20