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	$219.53	6.557%	$233.9246	$233.92	$233.90	$233.90
Purchase #2	$242.94	11.138%	$269.9987	$270.00	$270.00	$270.00
Purchase #3	$10.41	6.464%	$11.0829	$11.08	$11.10	$11.10
Purchase #4	$95.37	5.136%	$100.2682	$100.27	$100.25	$100.30
Purchase #5	$18.84	7.126%	$20.1825	$20.18	$20.20	$20.20
Purchase #6	$71.74	6.143%	$76.147	$76.15	$76.15	$76.10
Purchase #7	$28.88	13.512%	$32.7823	$32.78	$32.80	$32.80
7 purchase totals =	$687.71		$744.3862	$744.38	$744.40	$744.40