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	$100.36	5.118%	$105.4964	$105.50	$105.50	$105.50
Purchase #2	$48.41	11.599%	$54.0251	$54.03	$54.05	$54.00
Purchase #3	$173.93	12.752%	$196.1096	$196.11	$196.10	$196.10
Purchase #4	$116.25	5.375%	$122.4984	$122.50	$122.50	$122.50
Purchase #5	$231.87	6.782%	$247.5954	$247.60	$247.60	$247.60
Purchase #6	$198.41	9.115%	$216.4951	$216.50	$216.50	$216.50
Purchase #7	$108.25	3.655%	$112.2065	$112.21	$112.20	$112.20
7 purchase totals =	$977.48		$1,054.4265	$1,054.45	$1,054.45	$1,054.40