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	$101.64	4.196%	$105.9048	$105.90	$105.90	$105.90
Purchase #2	$236.42	6.382%	$251.5083	$251.51	$251.50	$251.50
Purchase #3	$9.56	6.734%	$10.2038	$10.20	$10.20	$10.20
Purchase #4	$36.39	8.862%	$39.6149	$39.61	$39.60	$39.60
Purchase #5	$153.90	9.555%	$168.6051	$168.61	$168.60	$168.60
Purchase #6	$228.98	9.464%	$250.6507	$250.65	$250.65	$250.70
Purchase #7	$134.76	13.242%	$152.6049	$152.60	$152.60	$152.60
7 purchase totals =	$901.65		$979.0925	$979.08	$979.05	$979.10