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	$106.28	11.312%	$118.3024	$118.30	$118.30	$118.30
Purchase #2	$98.45	5.551%	$103.915	$103.92	$103.90	$103.90
Purchase #3	$140.47	6.334%	$149.3674	$149.37	$149.35	$149.40
Purchase #4	$97.33	11.555%	$108.5765	$108.58	$108.60	$108.60
Purchase #5	$36.57	6.309%	$38.8772	$38.88	$38.90	$38.90
Purchase #6	$155.42	13.653%	$176.6395	$176.64	$176.65	$176.60
Purchase #7	$123.32	3.734%	$127.9248	$127.92	$127.90	$127.90
7 purchase totals =	$757.84		$823.6028	$823.61	$823.60	$823.60