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	$172.60	9.428%	$188.8727	$188.87	$188.85	$188.90
Purchase #2	$202.43	12.809%	$228.3593	$228.36	$228.35	$228.40
Purchase #3	$211.38	8.408%	$229.1528	$229.15	$229.15	$229.20
Purchase #4	$127.56	12.766%	$143.8443	$143.84	$143.85	$143.80
Purchase #5	$198.40	3.312%	$204.971	$204.97	$204.95	$205.00
Purchase #6	$35.59	6.254%	$37.8158	$37.82	$37.80	$37.80
Purchase #7	$143.60	11.346%	$159.8929	$159.89	$159.90	$159.90
7 purchase totals =	$1,091.56		$1,192.9088	$1,192.90	$1,192.85	$1,193.00