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	$17.63	9.180%	$19.2484	$19.25	$19.25	$19.20
Purchase #2	$38.73	7.866%	$41.7765	$41.78	$41.80	$41.80
Purchase #3	$245.95	7.639%	$264.7381	$264.74	$264.75	$264.70
Purchase #4	$72.61	8.304%	$78.6395	$78.64	$78.65	$78.60
Purchase #5	$66.66	12.359%	$74.8985	$74.90	$74.90	$74.90
Purchase #6	$78.72	3.441%	$81.4288	$81.43	$81.45	$81.40
Purchase #7	$127.84	7.636%	$137.6019	$137.60	$137.60	$137.60
7 purchase totals =	$648.14		$698.3317	$698.34	$698.40	$698.20