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	$171.36	11.380%	$190.8608	$190.86	$190.85	$190.90
Purchase #2	$171.74	9.532%	$188.1103	$188.11	$188.10	$188.10
Purchase #3	$118.68	12.336%	$133.3204	$133.32	$133.30	$133.30
Purchase #4	$18.42	9.303%	$20.1336	$20.13	$20.15	$20.10
Purchase #5	$220.82	13.789%	$251.2689	$251.27	$251.25	$251.30
Purchase #6	$222.48	3.147%	$229.4814	$229.48	$229.50	$229.50
Purchase #7	$31.41	4.472%	$32.8147	$32.81	$32.80	$32.80
7 purchase totals =	$954.91		$1,045.9901	$1,045.98	$1,045.95	$1,046.00