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	$38.76	6.806%	$41.398	$41.40	$41.40	$41.40
Purchase #2	$183.69	6.719%	$196.0321	$196.03	$196.05	$196.00
Purchase #3	$137.43	10.716%	$152.157	$152.16	$152.15	$152.20
Purchase #4	$203.58	6.177%	$216.1551	$216.16	$216.15	$216.20
Purchase #5	$142.61	5.508%	$150.465	$150.47	$150.45	$150.50
Purchase #6	$132.59	9.834%	$145.6289	$145.63	$145.65	$145.60
Purchase #7	$186.88	10.397%	$206.3099	$206.31	$206.30	$206.30
7 purchase totals =	$1,025.54		$1,108.1460	$1,108.16	$1,108.15	$1,108.20