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	$193.59	13.788%	$220.2822	$220.28	$220.30	$220.30
Purchase #2	$24.37	6.188%	$25.878	$25.88	$25.90	$25.90
Purchase #3	$144.47	9.851%	$158.7017	$158.70	$158.70	$158.70
Purchase #4	$220.42	10.701%	$244.0071	$244.01	$244.00	$244.00
Purchase #5	$59.72	10.184%	$65.8019	$65.80	$65.80	$65.80
Purchase #6	$34.55	8.325%	$37.4263	$37.43	$37.45	$37.40
Purchase #7	$96.68	3.148%	$99.7235	$99.72	$99.70	$99.70
7 purchase totals =	$773.80		$851.8207	$851.82	$851.85	$851.80