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	$149.26	12.356%	$167.7026	$167.70	$167.70	$167.70
Purchase #2	$118.59	10.543%	$131.0929	$131.09	$131.10	$131.10
Purchase #3	$146.37	10.708%	$162.0433	$162.04	$162.05	$162.00
Purchase #4	$107.88	3.581%	$111.7432	$111.74	$111.75	$111.70
Purchase #5	$61.86	6.857%	$66.1017	$66.10	$66.10	$66.10
Purchase #6	$147.77	8.655%	$160.5595	$160.56	$160.55	$160.60
Purchase #7	$210.90	12.563%	$237.3954	$237.40	$237.40	$237.40
7 purchase totals =	$942.63		$1,036.6386	$1,036.63	$1,036.65	$1,036.60