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	$134.25	5.381%	$141.474	$141.47	$141.45	$141.50
Purchase #2	$43.44	5.220%	$45.7076	$45.71	$45.70	$45.70
Purchase #3	$234.30	3.367%	$242.1889	$242.19	$242.20	$242.20
Purchase #4	$50.28	4.182%	$52.3827	$52.38	$52.40	$52.40
Purchase #5	$45.92	10.591%	$50.7834	$50.78	$50.80	$50.80
Purchase #6	$235.27	6.657%	$250.9319	$250.93	$250.95	$250.90
Purchase #7	$103.97	10.495%	$114.8817	$114.88	$114.90	$114.90
7 purchase totals =	$847.43		$898.3502	$898.34	$898.40	$898.40