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	$150.51	12.444%	$169.2395	$169.24	$169.25	$169.20
Purchase #2	$86.61	13.648%	$98.4305	$98.43	$98.45	$98.40
Purchase #3	$134.51	5.715%	$142.1972	$142.20	$142.20	$142.20
Purchase #4	$64.28	3.344%	$66.4295	$66.43	$66.45	$66.40
Purchase #5	$164.58	9.126%	$179.5996	$179.60	$179.60	$179.60
Purchase #6	$97.54	5.843%	$103.2393	$103.24	$103.25	$103.20
Purchase #7	$102.41	10.566%	$113.2306	$113.23	$113.25	$113.20
7 purchase totals =	$800.44		$872.3662	$872.37	$872.45	$872.20