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	$211.66	10.134%	$233.1096	$233.11	$233.10	$233.10
Purchase #2	$65.99	10.507%	$72.9236	$72.92	$72.90	$72.90
Purchase #3	$68.37	3.263%	$70.6009	$70.60	$70.60	$70.60
Purchase #4	$30.32	9.382%	$33.1646	$33.16	$33.15	$33.20
Purchase #5	$50.39	10.309%	$55.5847	$55.58	$55.60	$55.60
Purchase #6	$85.51	6.574%	$91.1314	$91.13	$91.15	$91.10
Purchase #7	$34.29	7.449%	$36.8443	$36.84	$36.85	$36.80
7 purchase totals =	$546.53		$593.3591	$593.34	$593.35	$593.30