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	$173.89	5.138%	$182.8245	$182.82	$182.80	$182.80
Purchase #2	$91.46	4.115%	$95.2236	$95.22	$95.20	$95.20
Purchase #3	$223.37	4.387%	$233.1692	$233.17	$233.15	$233.20
Purchase #4	$50.36	7.504%	$54.139	$54.14	$54.15	$54.10
Purchase #5	$26.37	8.761%	$28.6803	$28.68	$28.70	$28.70
Purchase #6	$43.50	7.103%	$46.5898	$46.59	$46.60	$46.60
Purchase #7	$238.91	10.786%	$264.6788	$264.68	$264.70	$264.70
7 purchase totals =	$847.86		$905.3052	$905.30	$905.30	$905.30