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	$171.56	11.123%	$190.6426	$190.64	$190.65	$190.60
Purchase #2	$249.45	9.259%	$272.5466	$272.55	$272.55	$272.50
Purchase #3	$103.66	4.516%	$108.3413	$108.34	$108.35	$108.30
Purchase #4	$131.89	8.782%	$143.4726	$143.47	$143.45	$143.50
Purchase #5	$35.40	11.329%	$39.4105	$39.41	$39.40	$39.40
Purchase #6	$209.58	10.276%	$231.1164	$231.12	$231.10	$231.10
Purchase #7	$49.56	6.373%	$52.7185	$52.72	$52.70	$52.70
7 purchase totals =	$951.10		$1,038.2485	$1,038.25	$1,038.20	$1,038.10