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	$48.44	7.547%	$52.0958	$52.10	$52.10	$52.10
Purchase #2	$173.94	5.793%	$184.0163	$184.02	$184.00	$184.00
Purchase #3	$132.51	4.365%	$138.2941	$138.29	$138.30	$138.30
Purchase #4	$100.92	7.138%	$108.1237	$108.12	$108.10	$108.10
Purchase #5	$224.86	13.573%	$255.3802	$255.38	$255.40	$255.40
Purchase #6	$181.94	5.290%	$191.5646	$191.56	$191.55	$191.60
Purchase #7	$123.73	10.248%	$136.4099	$136.41	$136.40	$136.40
7 purchase totals =	$986.34		$1,065.8846	$1,065.88	$1,065.85	$1,065.90