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	$60.39	8.325%	$65.4175	$65.42	$65.40	$65.40
Purchase #2	$185.29	8.210%	$200.5023	$200.50	$200.50	$200.50
Purchase #3	$41.37	8.722%	$44.9783	$44.98	$45.00	$45.00
Purchase #4	$42.69	4.591%	$44.6499	$44.65	$44.65	$44.60
Purchase #5	$215.78	11.420%	$240.4221	$240.42	$240.40	$240.40
Purchase #6	$81.54	7.240%	$87.4435	$87.44	$87.45	$87.40
Purchase #7	$134.33	7.306%	$144.1441	$144.14	$144.15	$144.10
7 purchase totals =	$761.39		$827.5577	$827.55	$827.55	$827.40