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	$121.57	10.783%	$134.6789	$134.68	$134.70	$134.70
Purchase #2	$56.77	5.413%	$59.843	$59.84	$59.85	$59.80
Purchase #3	$212.35	4.678%	$222.2837	$222.28	$222.30	$222.30
Purchase #4	$127.66	13.263%	$144.5915	$144.59	$144.60	$144.60
Purchase #5	$57.65	11.819%	$64.4637	$64.46	$64.45	$64.50
Purchase #6	$173.79	10.711%	$192.4046	$192.40	$192.40	$192.40
Purchase #7	$95.92	7.231%	$102.856	$102.86	$102.85	$102.90
7 purchase totals =	$845.71		$921.1214	$921.11	$921.15	$921.20