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	$172.62	13.775%	$196.3984	$196.40	$196.40	$196.40
Purchase #2	$127.40	8.397%	$138.0978	$138.10	$138.10	$138.10
Purchase #3	$106.85	13.187%	$120.9403	$120.94	$120.95	$120.90
Purchase #4	$65.35	10.668%	$72.3215	$72.32	$72.30	$72.30
Purchase #5	$40.72	9.203%	$44.4675	$44.47	$44.45	$44.50
Purchase #6	$219.57	13.720%	$249.695	$249.70	$249.70	$249.70
Purchase #7	$148.51	7.666%	$159.8948	$159.89	$159.90	$159.90
7 purchase totals =	$881.02		$981.8153	$981.82	$981.80	$981.80