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	$160.37	8.154%	$173.4466	$173.45	$173.45	$173.40
Purchase #2	$49.69	7.712%	$53.5221	$53.52	$53.50	$53.50
Purchase #3	$53.29	12.505%	$59.9539	$59.95	$59.95	$60.00
Purchase #4	$200.42	10.319%	$221.1013	$221.10	$221.10	$221.10
Purchase #5	$152.76	13.363%	$173.1733	$173.17	$173.15	$173.20
Purchase #6	$241.33	3.342%	$249.3952	$249.40	$249.40	$249.40
Purchase #7	$60.47	8.549%	$65.6396	$65.64	$65.65	$65.60
7 purchase totals =	$918.33		$996.2320	$996.23	$996.20	$996.20