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	$142.26	10.673%	$157.4434	$157.44	$157.45	$157.40
Purchase #2	$17.27	12.637%	$19.4524	$19.45	$19.45	$19.50
Purchase #3	$50.78	10.553%	$56.1388	$56.14	$56.15	$56.10
Purchase #4	$57.78	13.187%	$65.3994	$65.40	$65.40	$65.40
Purchase #5	$151.52	3.872%	$157.3869	$157.39	$157.40	$157.40
Purchase #6	$50.34	10.820%	$55.7868	$55.79	$55.80	$55.80
Purchase #7	$43.39	4.556%	$45.3668	$45.37	$45.35	$45.40
7 purchase totals =	$513.34		$556.9745	$556.98	$557.00	$557.00