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	$40.44	7.435%	$43.4467	$43.45	$43.45	$43.40
Purchase #2	$155.37	9.317%	$169.8458	$169.85	$169.85	$169.80
Purchase #3	$173.32	8.248%	$187.6154	$187.62	$187.60	$187.60
Purchase #4	$126.83	8.668%	$137.8236	$137.82	$137.80	$137.80
Purchase #5	$130.37	13.617%	$148.1225	$148.12	$148.10	$148.10
Purchase #6	$162.85	4.768%	$170.6147	$170.61	$170.60	$170.60
Purchase #7	$221.41	5.575%	$233.7536	$233.75	$233.75	$233.80
7 purchase totals =	$1,010.59		$1,091.2223	$1,091.22	$1,091.15	$1,091.10