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	$41.67	9.419%	$45.5949	$45.59	$45.60	$45.60
Purchase #2	$31.65	5.300%	$33.3275	$33.33	$33.35	$33.30
Purchase #3	$198.53	10.804%	$219.9792	$219.98	$220.00	$220.00
Purchase #4	$66.74	3.635%	$69.166	$69.17	$69.15	$69.20
Purchase #5	$148.30	3.744%	$153.8524	$153.85	$153.85	$153.90
Purchase #6	$59.46	11.140%	$66.0838	$66.08	$66.10	$66.10
Purchase #7	$9.32	13.339%	$10.5632	$10.56	$10.55	$10.60
7 purchase totals =	$555.67		$598.5670	$598.56	$598.60	$598.70