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	$79.39	8.497%	$86.1358	$86.14	$86.15	$86.10
Purchase #2	$151.31	8.728%	$164.5163	$164.52	$164.50	$164.50
Purchase #3	$221.94	10.199%	$244.5757	$244.58	$244.60	$244.60
Purchase #4	$113.85	9.687%	$124.8786	$124.88	$124.90	$124.90
Purchase #5	$15.63	11.515%	$17.4298	$17.43	$17.45	$17.40
Purchase #6	$39.59	9.780%	$43.4619	$43.46	$43.45	$43.50
Purchase #7	$159.75	7.722%	$172.0859	$172.09	$172.10	$172.10
7 purchase totals =	$781.46		$853.0840	$853.10	$853.15	$853.10