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	$66.27	11.684%	$74.013	$74.01	$74.00	$74.00
Purchase #2	$237.89	13.684%	$270.4429	$270.44	$270.45	$270.40
Purchase #3	$185.87	7.387%	$199.6002	$199.60	$199.60	$199.60
Purchase #4	$119.81	6.714%	$127.854	$127.85	$127.85	$127.90
Purchase #5	$229.91	10.199%	$253.3585	$253.36	$253.35	$253.40
Purchase #6	$95.48	10.258%	$105.2743	$105.27	$105.25	$105.30
Purchase #7	$173.43	11.232%	$192.9097	$192.91	$192.90	$192.90
7 purchase totals =	$1,108.66		$1,223.4526	$1,223.44	$1,223.40	$1,223.50