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	$188.27	12.392%	$211.6004	$211.60	$211.60	$211.60
Purchase #2	$5.96	3.196%	$6.1505	$6.15	$6.15	$6.20
Purchase #3	$241.85	9.239%	$264.1945	$264.19	$264.20	$264.20
Purchase #4	$63.25	11.619%	$70.599	$70.60	$70.60	$70.60
Purchase #5	$236.56	12.699%	$266.6008	$266.60	$266.60	$266.60
Purchase #6	$172.25	6.725%	$183.8338	$183.83	$183.85	$183.80
Purchase #7	$48.40	11.530%	$53.9805	$53.98	$54.00	$54.00
7 purchase totals =	$956.54		$1,056.9595	$1,056.95	$1,057.00	$1,057.00