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	$65.55	3.382%	$67.7669	$67.77	$67.75	$67.80
Purchase #2	$66.53	8.805%	$72.388	$72.39	$72.40	$72.40
Purchase #3	$162.31	3.350%	$167.7474	$167.75	$167.75	$167.70
Purchase #4	$193.56	7.204%	$207.5041	$207.50	$207.50	$207.50
Purchase #5	$5.80	5.524%	$6.1204	$6.12	$6.10	$6.10
Purchase #6	$228.79	4.215%	$238.4335	$238.43	$238.45	$238.40
Purchase #7	$82.60	10.680%	$91.4217	$91.42	$91.40	$91.40
7 purchase totals =	$805.14		$851.3820	$851.38	$851.35	$851.30