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	$199.37	12.798%	$224.8854	$224.89	$224.90	$224.90
Purchase #2	$56.60	9.469%	$61.9595	$61.96	$61.95	$62.00
Purchase #3	$140.55	7.701%	$151.3738	$151.37	$151.35	$151.40
Purchase #4	$114.57	11.138%	$127.3308	$127.33	$127.35	$127.30
Purchase #5	$185.27	5.312%	$195.1115	$195.11	$195.10	$195.10
Purchase #6	$107.86	10.255%	$118.921	$118.92	$118.90	$118.90
Purchase #7	$75.99	9.160%	$82.9507	$82.95	$82.95	$83.00
7 purchase totals =	$880.21		$962.5327	$962.53	$962.50	$962.60