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	$18.69	5.689%	$19.7533	$19.75	$19.75	$19.80
Purchase #2	$225.35	7.168%	$241.5031	$241.50	$241.50	$241.50
Purchase #3	$127.38	13.309%	$144.333	$144.33	$144.35	$144.30
Purchase #4	$100.29	11.237%	$111.5596	$111.56	$111.55	$111.60
Purchase #5	$70.45	7.350%	$75.6281	$75.63	$75.65	$75.60
Purchase #6	$170.63	11.591%	$190.4077	$190.41	$190.40	$190.40
Purchase #7	$96.87	6.676%	$103.337	$103.34	$103.35	$103.30
7 purchase totals =	$809.66		$886.5218	$886.52	$886.55	$886.50