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	$176.75	3.491%	$182.9203	$182.92	$182.90	$182.90
Purchase #2	$191.95	9.637%	$210.4482	$210.45	$210.45	$210.40
Purchase #3	$135.49	5.141%	$142.4555	$142.46	$142.45	$142.50
Purchase #4	$52.51	6.484%	$55.9147	$55.91	$55.90	$55.90
Purchase #5	$160.63	4.848%	$168.4173	$168.42	$168.40	$168.40
Purchase #6	$183.79	11.589%	$205.0894	$205.09	$205.10	$205.10
Purchase #7	$223.80	11.784%	$250.1726	$250.17	$250.15	$250.20
7 purchase totals =	$1,124.92		$1,215.4180	$1,215.42	$1,215.35	$1,215.40