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	$24.40	11.607%	$27.2321	$27.23	$27.25	$27.20
Purchase #2	$162.26	11.161%	$180.3698	$180.37	$180.35	$180.40
Purchase #3	$73.49	12.829%	$82.918	$82.92	$82.90	$82.90
Purchase #4	$99.57	6.710%	$106.2511	$106.25	$106.25	$106.30
Purchase #5	$173.52	13.795%	$197.4571	$197.46	$197.45	$197.50
Purchase #6	$237.82	4.647%	$248.8715	$248.87	$248.85	$248.90
Purchase #7	$168.95	4.341%	$176.2841	$176.28	$176.30	$176.30
7 purchase totals =	$940.01		$1,019.3837	$1,019.38	$1,019.35	$1,019.50