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	$109.56	8.474%	$118.8441	$118.84	$118.85	$118.80
Purchase #2	$246.38	3.247%	$254.38	$254.38	$254.40	$254.40
Purchase #3	$63.62	4.645%	$66.5751	$66.58	$66.60	$66.60
Purchase #4	$70.91	13.420%	$80.4261	$80.43	$80.45	$80.40
Purchase #5	$78.34	8.620%	$85.0929	$85.09	$85.10	$85.10
Purchase #6	$137.45	11.687%	$153.5138	$153.51	$153.50	$153.50
Purchase #7	$84.77	6.559%	$90.3301	$90.33	$90.35	$90.30
7 purchase totals =	$791.03		$849.1621	$849.16	$849.25	$849.10