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	$117.73	5.197%	$123.8484	$123.85	$123.85	$123.80
Purchase #2	$103.93	11.811%	$116.2052	$116.21	$116.20	$116.20
Purchase #3	$71.94	4.142%	$74.9198	$74.92	$74.90	$74.90
Purchase #4	$49.39	5.575%	$52.1435	$52.14	$52.15	$52.10
Purchase #5	$138.38	5.231%	$145.6187	$145.62	$145.60	$145.60
Purchase #6	$220.30	13.855%	$250.8226	$250.82	$250.80	$250.80
Purchase #7	$247.88	9.497%	$271.4212	$271.42	$271.40	$271.40
7 purchase totals =	$949.55		$1,034.9794	$1,034.98	$1,034.90	$1,034.80