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	$99.86	5.405%	$105.2574	$105.26	$105.25	$105.30
Purchase #2	$20.76	10.429%	$22.9251	$22.93	$22.95	$22.90
Purchase #3	$13.49	11.568%	$15.0505	$15.05	$15.05	$15.10
Purchase #4	$106.78	4.406%	$111.4847	$111.48	$111.50	$111.50
Purchase #5	$209.73	12.380%	$235.6946	$235.69	$235.70	$235.70
Purchase #6	$218.45	12.510%	$245.7781	$245.78	$245.80	$245.80
Purchase #7	$18.63	7.503%	$20.0278	$20.03	$20.05	$20.00
7 purchase totals =	$687.70		$756.2182	$756.22	$756.30	$756.30