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	$132.40	7.140%	$141.8534	$141.85	$141.85	$141.90
Purchase #2	$28.27	11.133%	$31.4173	$31.42	$31.40	$31.40
Purchase #3	$153.57	5.766%	$162.4248	$162.42	$162.40	$162.40
Purchase #4	$104.86	8.813%	$114.1013	$114.10	$114.10	$114.10
Purchase #5	$225.49	12.198%	$252.9953	$253.00	$253.00	$253.00
Purchase #6	$211.34	3.864%	$219.5062	$219.51	$219.50	$219.50
Purchase #7	$188.68	6.481%	$200.9084	$200.91	$200.90	$200.90
7 purchase totals =	$1,044.61		$1,123.2067	$1,123.21	$1,123.15	$1,123.20