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	$47.68	5.635%	$50.3668	$50.37	$50.35	$50.40
Purchase #2	$169.39	5.678%	$179.008	$179.01	$179.00	$179.00
Purchase #3	$103.46	7.707%	$111.4337	$111.43	$111.45	$111.40
Purchase #4	$173.30	13.652%	$196.9589	$196.96	$196.95	$197.00
Purchase #5	$85.30	6.440%	$90.7933	$90.79	$90.80	$90.80
Purchase #6	$225.48	12.200%	$252.9886	$252.99	$253.00	$253.00
Purchase #7	$236.60	10.498%	$261.4383	$261.44	$261.45	$261.40
7 purchase totals =	$1,041.21		$1,142.9876	$1,142.99	$1,143.00	$1,143.00