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	$76.88	11.176%	$85.4721	$85.47	$85.45	$85.50
Purchase #2	$186.73	12.342%	$209.7762	$209.78	$209.80	$209.80
Purchase #3	$32.47	7.238%	$34.8202	$34.82	$34.80	$34.80
Purchase #4	$60.43	8.568%	$65.6076	$65.61	$65.60	$65.60
Purchase #5	$147.85	3.696%	$153.3145	$153.31	$153.30	$153.30
Purchase #6	$208.51	12.531%	$234.6384	$234.64	$234.65	$234.60
Purchase #7	$243.92	11.408%	$271.7464	$271.75	$271.75	$271.70
7 purchase totals =	$956.79		$1,055.3754	$1,055.38	$1,055.35	$1,055.30