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	$214.61	5.829%	$227.1196	$227.12	$227.10	$227.10
Purchase #2	$27.47	10.287%	$30.2958	$30.30	$30.30	$30.30
Purchase #3	$44.38	3.703%	$46.0234	$46.02	$46.00	$46.00
Purchase #4	$111.57	10.762%	$123.5772	$123.58	$123.60	$123.60
Purchase #5	$168.78	9.485%	$184.7888	$184.79	$184.80	$184.80
Purchase #6	$32.77	9.343%	$35.8317	$35.83	$35.85	$35.80
Purchase #7	$65.58	8.739%	$71.311	$71.31	$71.30	$71.30
7 purchase totals =	$665.16		$718.9475	$718.95	$718.95	$718.90