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	$176.76	8.575%	$191.9172	$191.92	$191.90	$191.90
Purchase #2	$139.52	11.461%	$155.5104	$155.51	$155.50	$155.50
Purchase #3	$157.82	5.542%	$166.5664	$166.57	$166.55	$166.60
Purchase #4	$94.42	7.688%	$101.679	$101.68	$101.70	$101.70
Purchase #5	$11.88	10.655%	$13.1458	$13.15	$13.15	$13.10
Purchase #6	$199.46	10.205%	$219.8149	$219.81	$219.80	$219.80
Purchase #7	$164.59	4.554%	$172.0854	$172.09	$172.10	$172.10
7 purchase totals =	$944.45		$1,020.7191	$1,020.73	$1,020.70	$1,020.70