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	$128.29	13.760%	$145.9427	$145.94	$145.95	$145.90
Purchase #2	$144.68	11.657%	$161.5453	$161.55	$161.55	$161.50
Purchase #3	$161.34	11.358%	$179.665	$179.67	$179.65	$179.70
Purchase #4	$16.99	5.243%	$17.8808	$17.88	$17.90	$17.90
Purchase #5	$82.33	4.329%	$85.8941	$85.89	$85.90	$85.90
Purchase #6	$233.89	7.695%	$251.8878	$251.89	$251.90	$251.90
Purchase #7	$229.62	6.521%	$244.5935	$244.59	$244.60	$244.60
7 purchase totals =	$997.14		$1,087.4092	$1,087.41	$1,087.45	$1,087.40