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	$56.34	11.190%	$62.6444	$62.64	$62.65	$62.60
Purchase #2	$35.92	3.268%	$37.0939	$37.09	$37.10	$37.10
Purchase #3	$171.53	7.789%	$184.8905	$184.89	$184.90	$184.90
Purchase #4	$41.74	3.673%	$43.2731	$43.27	$43.25	$43.30
Purchase #5	$21.99	9.525%	$24.0845	$24.08	$24.10	$24.10
Purchase #6	$135.72	6.717%	$144.8363	$144.84	$144.85	$144.80
Purchase #7	$61.53	7.772%	$66.3121	$66.31	$66.30	$66.30
7 purchase totals =	$524.77		$563.1348	$563.12	$563.15	$563.10