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	$35.55	13.681%	$40.4136	$40.41	$40.40	$40.40
Purchase #2	$205.25	13.588%	$233.1394	$233.14	$233.15	$233.10
Purchase #3	$153.55	11.110%	$170.6094	$170.61	$170.60	$170.60
Purchase #4	$9.79	5.557%	$10.334	$10.33	$10.35	$10.30
Purchase #5	$83.52	3.509%	$86.4507	$86.45	$86.45	$86.50
Purchase #6	$88.53	8.839%	$96.3552	$96.36	$96.35	$96.40
Purchase #7	$232.82	6.764%	$248.5679	$248.57	$248.55	$248.60
7 purchase totals =	$809.01		$885.8702	$885.87	$885.85	$885.90