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	$99.51	12.448%	$111.897	$111.90	$111.90	$111.90
Purchase #2	$175.42	4.395%	$183.1297	$183.13	$183.15	$183.10
Purchase #3	$27.94	11.222%	$31.0754	$31.08	$31.10	$31.10
Purchase #4	$131.32	5.825%	$138.9694	$138.97	$138.95	$139.00
Purchase #5	$94.33	10.805%	$104.5224	$104.52	$104.50	$104.50
Purchase #6	$243.47	11.761%	$272.1045	$272.10	$272.10	$272.10
Purchase #7	$233.93	12.373%	$262.8742	$262.87	$262.85	$262.90
7 purchase totals =	$1,005.92		$1,104.5726	$1,104.57	$1,104.55	$1,104.60