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	$214.28	13.571%	$243.3599	$243.36	$243.35	$243.40
Purchase #2	$42.39	9.596%	$46.4577	$46.46	$46.45	$46.50
Purchase #3	$224.86	5.177%	$236.501	$236.50	$236.50	$236.50
Purchase #4	$164.54	4.202%	$171.454	$171.45	$171.45	$171.50
Purchase #5	$32.82	11.494%	$36.5923	$36.59	$36.60	$36.60
Purchase #6	$89.56	10.757%	$99.194	$99.19	$99.20	$99.20
Purchase #7	$151.78	9.160%	$165.683	$165.68	$165.70	$165.70
7 purchase totals =	$920.23		$999.2419	$999.23	$999.25	$999.40