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	$210.47	3.723%	$218.3058	$218.31	$218.30	$218.30
Purchase #2	$155.62	6.347%	$165.4972	$165.50	$165.50	$165.50
Purchase #3	$74.29	3.124%	$76.6108	$76.61	$76.60	$76.60
Purchase #4	$202.67	4.407%	$211.6017	$211.60	$211.60	$211.60
Purchase #5	$113.62	11.784%	$127.009	$127.01	$127.00	$127.00
Purchase #6	$73.99	12.267%	$83.0664	$83.07	$83.05	$83.10
Purchase #7	$114.68	7.563%	$123.3532	$123.35	$123.35	$123.40
7 purchase totals =	$945.34		$1,005.4441	$1,005.45	$1,005.40	$1,005.50