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	$155.80	10.607%	$172.3257	$172.33	$172.35	$172.30
Purchase #2	$167.91	3.111%	$173.1337	$173.13	$173.15	$173.10
Purchase #3	$102.42	10.588%	$113.2642	$113.26	$113.25	$113.30
Purchase #4	$117.50	10.711%	$130.0854	$130.09	$130.10	$130.10
Purchase #5	$109.97	9.613%	$120.5414	$120.54	$120.55	$120.50
Purchase #6	$108.76	13.412%	$123.3469	$123.35	$123.35	$123.30
Purchase #7	$116.90	12.163%	$131.1185	$131.12	$131.10	$131.10
7 purchase totals =	$879.26		$963.8158	$963.82	$963.85	$963.70