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	$186.61	4.422%	$194.8619	$194.86	$194.85	$194.90
Purchase #2	$139.44	3.286%	$144.022	$144.02	$144.00	$144.00
Purchase #3	$120.40	11.776%	$134.5783	$134.58	$134.60	$134.60
Purchase #4	$109.37	6.786%	$116.7918	$116.79	$116.80	$116.80
Purchase #5	$116.64	10.768%	$129.1998	$129.20	$129.20	$129.20
Purchase #6	$68.89	3.871%	$71.5567	$71.56	$71.55	$71.60
Purchase #7	$9.82	10.477%	$10.8488	$10.85	$10.85	$10.80
7 purchase totals =	$751.17		$801.8593	$801.86	$801.85	$801.90