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	$189.68	7.304%	$203.5342	$203.53	$203.55	$203.50
Purchase #2	$148.26	13.586%	$168.4026	$168.40	$168.40	$168.40
Purchase #3	$167.31	13.868%	$190.5126	$190.51	$190.50	$190.50
Purchase #4	$117.59	8.506%	$127.5922	$127.59	$127.60	$127.60
Purchase #5	$248.77	11.537%	$277.4706	$277.47	$277.45	$277.50
Purchase #6	$246.91	4.125%	$257.095	$257.10	$257.10	$257.10
Purchase #7	$198.76	10.367%	$219.3654	$219.37	$219.35	$219.40
7 purchase totals =	$1,317.28		$1,443.9726	$1,443.97	$1,443.95	$1,444.00