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	$65.32	9.744%	$71.6848	$71.68	$71.70	$71.70
Purchase #2	$101.78	3.291%	$105.1296	$105.13	$105.15	$105.10
Purchase #3	$193.81	5.304%	$204.0897	$204.09	$204.10	$204.10
Purchase #4	$32.52	10.199%	$35.8367	$35.84	$35.85	$35.80
Purchase #5	$149.53	4.664%	$156.5041	$156.50	$156.50	$156.50
Purchase #6	$217.39	7.356%	$233.3812	$233.38	$233.40	$233.40
Purchase #7	$249.97	11.644%	$279.0765	$279.08	$279.10	$279.10
7 purchase totals =	$1,010.32		$1,085.7026	$1,085.70	$1,085.80	$1,085.70