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	$100.45	4.455%	$104.925	$104.93	$104.95	$104.90
Purchase #2	$133.74	9.839%	$146.8987	$146.90	$146.90	$146.90
Purchase #3	$95.79	3.443%	$99.088	$99.09	$99.10	$99.10
Purchase #4	$69.63	13.605%	$79.1032	$79.10	$79.10	$79.10
Purchase #5	$14.56	12.707%	$16.4101	$16.41	$16.40	$16.40
Purchase #6	$26.30	4.762%	$27.5524	$27.55	$27.55	$27.60
Purchase #7	$250.69	5.526%	$264.5431	$264.54	$264.55	$264.50
7 purchase totals =	$691.16		$738.5205	$738.52	$738.55	$738.50