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	$217.40	4.623%	$227.4504	$227.45	$227.45	$227.50
Purchase #2	$198.61	8.161%	$214.8186	$214.82	$214.80	$214.80
Purchase #3	$52.72	10.333%	$58.1676	$58.17	$58.15	$58.20
Purchase #4	$76.88	11.476%	$85.7027	$85.70	$85.70	$85.70
Purchase #5	$147.44	3.470%	$152.5562	$152.56	$152.55	$152.60
Purchase #6	$49.39	8.270%	$53.4746	$53.47	$53.45	$53.50
Purchase #7	$98.89	12.854%	$111.6013	$111.60	$111.60	$111.60
7 purchase totals =	$841.33		$903.7714	$903.77	$903.70	$903.90