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	$35.48	4.860%	$37.2043	$37.20	$37.20	$37.20
Purchase #2	$39.91	8.363%	$43.2477	$43.25	$43.25	$43.20
Purchase #3	$141.64	8.610%	$153.8352	$153.84	$153.85	$153.80
Purchase #4	$79.96	10.824%	$88.6149	$88.61	$88.60	$88.60
Purchase #5	$95.31	13.724%	$108.3903	$108.39	$108.40	$108.40
Purchase #6	$41.57	9.579%	$45.552	$45.55	$45.55	$45.60
Purchase #7	$90.88	3.819%	$94.3507	$94.35	$94.35	$94.40
7 purchase totals =	$524.75		$571.1951	$571.19	$571.20	$571.20