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	$40.82	11.407%	$45.4763	$45.48	$45.50	$45.50
Purchase #2	$59.42	7.730%	$64.0132	$64.01	$64.00	$64.00
Purchase #3	$74.68	4.560%	$78.0854	$78.09	$78.10	$78.10
Purchase #4	$86.88	11.186%	$96.5984	$96.60	$96.60	$96.60
Purchase #5	$146.59	3.219%	$151.3087	$151.31	$151.30	$151.30
Purchase #6	$41.92	7.229%	$44.9504	$44.95	$44.95	$45.00
Purchase #7	$233.45	12.716%	$263.1355	$263.14	$263.15	$263.10
7 purchase totals =	$683.76		$743.5679	$743.58	$743.60	$743.60