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	$130.58	3.191%	$134.7468	$134.75	$134.75	$134.70
Purchase #2	$53.43	11.220%	$59.4248	$59.42	$59.40	$59.40
Purchase #3	$164.69	4.472%	$172.0549	$172.05	$172.05	$172.10
Purchase #4	$104.60	7.844%	$112.8048	$112.80	$112.80	$112.80
Purchase #5	$48.67	6.597%	$51.8808	$51.88	$51.90	$51.90
Purchase #6	$244.52	3.484%	$253.0391	$253.04	$253.05	$253.00
Purchase #7	$59.31	13.709%	$67.4408	$67.44	$67.45	$67.40
7 purchase totals =	$805.80		$851.3920	$851.38	$851.40	$851.30