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	$173.52	4.223%	$180.8477	$180.85	$180.85	$180.80
Purchase #2	$159.61	11.806%	$178.4536	$178.45	$178.45	$178.50
Purchase #3	$75.94	10.436%	$83.8651	$83.87	$83.85	$83.90
Purchase #4	$247.44	5.850%	$261.9152	$261.92	$261.90	$261.90
Purchase #5	$156.64	11.260%	$174.2777	$174.28	$174.30	$174.30
Purchase #6	$138.92	12.722%	$156.5934	$156.59	$156.60	$156.60
Purchase #7	$112.32	6.664%	$119.805	$119.81	$119.80	$119.80
7 purchase totals =	$1,064.39		$1,155.7577	$1,155.77	$1,155.75	$1,155.80