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	$20.78	7.838%	$22.4087	$22.41	$22.40	$22.40
Purchase #2	$75.63	13.540%	$85.8703	$85.87	$85.85	$85.90
Purchase #3	$94.43	7.433%	$101.449	$101.45	$101.45	$101.40
Purchase #4	$20.53	11.495%	$22.8899	$22.89	$22.90	$22.90
Purchase #5	$155.56	8.562%	$168.879	$168.88	$168.90	$168.90
Purchase #6	$41.73	5.395%	$43.9813	$43.98	$44.00	$44.00
Purchase #7	$150.86	3.285%	$155.8158	$155.82	$155.80	$155.80
7 purchase totals =	$559.52		$601.2940	$601.30	$601.30	$601.30