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	$132.89	8.198%	$143.7843	$143.78	$143.80	$143.80
Purchase #2	$159.94	5.454%	$168.6631	$168.66	$168.65	$168.70
Purchase #3	$32.87	6.134%	$34.8862	$34.89	$34.90	$34.90
Purchase #4	$79.53	3.824%	$82.5712	$82.57	$82.55	$82.60
Purchase #5	$238.70	7.842%	$257.4189	$257.42	$257.40	$257.40
Purchase #6	$206.49	13.281%	$233.9139	$233.91	$233.90	$233.90
Purchase #7	$214.85	11.746%	$240.0863	$240.09	$240.10	$240.10
7 purchase totals =	$1,065.27		$1,161.3239	$1,161.32	$1,161.30	$1,161.40