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	$33.86	10.318%	$37.3537	$37.35	$37.35	$37.40
Purchase #2	$39.35	13.768%	$44.7677	$44.77	$44.75	$44.80
Purchase #3	$87.26	3.637%	$90.4336	$90.43	$90.45	$90.40
Purchase #4	$14.46	10.289%	$15.9478	$15.95	$15.95	$15.90
Purchase #5	$224.55	10.263%	$247.5956	$247.60	$247.60	$247.60
Purchase #6	$131.72	11.479%	$146.8401	$146.84	$146.85	$146.80
Purchase #7	$250.52	3.483%	$259.2456	$259.25	$259.25	$259.20
7 purchase totals =	$781.72		$842.1841	$842.19	$842.20	$842.10