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	$176.51	5.747%	$186.654	$186.65	$186.65	$186.70
Purchase #2	$92.31	8.237%	$99.9136	$99.91	$99.90	$99.90
Purchase #3	$134.83	3.478%	$139.5194	$139.52	$139.50	$139.50
Purchase #4	$133.77	12.442%	$150.4137	$150.41	$150.40	$150.40
Purchase #5	$151.61	3.846%	$157.4409	$157.44	$157.45	$157.40
Purchase #6	$143.93	10.111%	$158.4828	$158.48	$158.50	$158.50
Purchase #7	$22.34	8.393%	$24.215	$24.22	$24.20	$24.20
7 purchase totals =	$855.30		$916.6394	$916.63	$916.60	$916.60