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	$144.34	11.268%	$160.6042	$160.60	$160.60	$160.60
Purchase #2	$233.76	6.468%	$248.8796	$248.88	$248.90	$248.90
Purchase #3	$51.41	6.646%	$54.8267	$54.83	$54.85	$54.80
Purchase #4	$150.52	12.784%	$169.7625	$169.76	$169.75	$169.80
Purchase #5	$228.28	6.193%	$242.4174	$242.42	$242.40	$242.40
Purchase #6	$159.94	6.611%	$170.5136	$170.51	$170.50	$170.50
Purchase #7	$6.69	8.300%	$7.2453	$7.25	$7.25	$7.20
7 purchase totals =	$974.94		$1,054.2493	$1,054.25	$1,054.25	$1,054.20