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	$235.32	4.234%	$245.2834	$245.28	$245.30	$245.30
Purchase #2	$155.99	11.195%	$173.4531	$173.45	$173.45	$173.50
Purchase #3	$36.55	11.706%	$40.8285	$40.83	$40.85	$40.80
Purchase #4	$152.45	9.832%	$167.4389	$167.44	$167.45	$167.40
Purchase #5	$59.93	8.829%	$65.2212	$65.22	$65.20	$65.20
Purchase #6	$17.31	6.412%	$18.4199	$18.42	$18.40	$18.40
Purchase #7	$249.52	10.839%	$276.5655	$276.57	$276.55	$276.60
7 purchase totals =	$907.07		$987.2105	$987.21	$987.20	$987.20