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	$210.27	5.508%	$221.8517	$221.85	$221.85	$221.90
Purchase #2	$221.96	3.452%	$229.6221	$229.62	$229.60	$229.60
Purchase #3	$76.67	11.359%	$85.3789	$85.38	$85.40	$85.40
Purchase #4	$122.58	3.837%	$127.2834	$127.28	$127.30	$127.30
Purchase #5	$249.60	8.696%	$271.3052	$271.31	$271.30	$271.30
Purchase #6	$234.34	4.616%	$245.1571	$245.16	$245.15	$245.20
Purchase #7	$118.50	11.342%	$131.9403	$131.94	$131.95	$131.90
7 purchase totals =	$1,233.92		$1,312.5387	$1,312.54	$1,312.55	$1,312.60