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	$184.90	13.354%	$209.5915	$209.59	$209.60	$209.60
Purchase #2	$94.92	4.677%	$99.3594	$99.36	$99.35	$99.40
Purchase #3	$238.27	3.721%	$247.136	$247.14	$247.15	$247.10
Purchase #4	$183.39	4.832%	$192.2514	$192.25	$192.25	$192.30
Purchase #5	$205.32	7.714%	$221.1584	$221.16	$221.15	$221.20
Purchase #6	$220.59	10.855%	$244.535	$244.54	$244.55	$244.50
Purchase #7	$157.25	8.386%	$170.437	$170.44	$170.45	$170.40
7 purchase totals =	$1,284.64		$1,384.4687	$1,384.48	$1,384.50	$1,384.50