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	$225.81	13.851%	$257.0869	$257.09	$257.10	$257.10
Purchase #2	$126.74	4.710%	$132.7095	$132.71	$132.70	$132.70
Purchase #3	$170.38	8.347%	$184.6016	$184.60	$184.60	$184.60
Purchase #4	$114.36	10.582%	$126.4616	$126.46	$126.45	$126.50
Purchase #5	$68.35	4.438%	$71.3834	$71.38	$71.40	$71.40
Purchase #6	$96.30	13.521%	$109.3207	$109.32	$109.30	$109.30
Purchase #7	$199.66	11.233%	$222.0878	$222.09	$222.10	$222.10
7 purchase totals =	$1,001.60		$1,103.6515	$1,103.65	$1,103.65	$1,103.70