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	$192.30	6.741%	$205.2629	$205.26	$205.25	$205.30
Purchase #2	$191.38	10.385%	$211.2548	$211.25	$211.25	$211.30
Purchase #3	$152.91	11.385%	$170.3188	$170.32	$170.30	$170.30
Purchase #4	$136.46	11.738%	$152.4777	$152.48	$152.50	$152.50
Purchase #5	$73.29	6.316%	$77.919	$77.92	$77.90	$77.90
Purchase #6	$12.81	10.373%	$14.1388	$14.14	$14.15	$14.10
Purchase #7	$146.31	13.794%	$166.492	$166.49	$166.50	$166.50
7 purchase totals =	$905.46		$997.8640	$997.86	$997.85	$997.90