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	$162.97	6.656%	$173.8173	$173.82	$173.80	$173.80
Purchase #2	$138.36	6.829%	$147.8086	$147.81	$147.80	$147.80
Purchase #3	$122.93	7.838%	$132.5653	$132.57	$132.55	$132.60
Purchase #4	$60.41	3.699%	$62.6446	$62.64	$62.65	$62.60
Purchase #5	$144.77	5.611%	$152.893	$152.89	$152.90	$152.90
Purchase #6	$109.71	12.563%	$123.4929	$123.49	$123.50	$123.50
Purchase #7	$249.49	4.764%	$261.3757	$261.38	$261.40	$261.40
7 purchase totals =	$988.64		$1,054.5974	$1,054.60	$1,054.60	$1,054.60