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	$94.94	8.837%	$103.3298	$103.33	$103.35	$103.30
Purchase #2	$85.81	3.210%	$88.5645	$88.56	$88.55	$88.60
Purchase #3	$175.86	5.858%	$186.1619	$186.16	$186.15	$186.20
Purchase #4	$54.83	5.588%	$57.8939	$57.89	$57.90	$57.90
Purchase #5	$242.31	8.793%	$263.6163	$263.62	$263.60	$263.60
Purchase #6	$129.74	13.202%	$146.8683	$146.87	$146.85	$146.90
Purchase #7	$151.54	10.720%	$167.7851	$167.79	$167.80	$167.80
7 purchase totals =	$935.03		$1,014.2198	$1,014.22	$1,014.20	$1,014.30