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	$146.98	13.310%	$166.543	$166.54	$166.55	$166.50
Purchase #2	$102.61	8.659%	$111.495	$111.50	$111.50	$111.50
Purchase #3	$166.61	8.129%	$180.1537	$180.15	$180.15	$180.20
Purchase #4	$205.81	11.691%	$229.8712	$229.87	$229.85	$229.90
Purchase #5	$19.98	12.727%	$22.5229	$22.52	$22.50	$22.50
Purchase #6	$200.64	13.390%	$227.5057	$227.51	$227.50	$227.50
Purchase #7	$83.52	8.471%	$90.595	$90.60	$90.60	$90.60
7 purchase totals =	$926.15		$1,028.6865	$1,028.69	$1,028.65	$1,028.70