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	$91.69	7.816%	$98.8565	$98.86	$98.85	$98.90
Purchase #2	$100.61	12.604%	$113.2909	$113.29	$113.30	$113.30
Purchase #3	$67.87	12.359%	$76.2581	$76.26	$76.25	$76.30
Purchase #4	$230.99	10.533%	$255.3202	$255.32	$255.30	$255.30
Purchase #5	$211.86	8.776%	$230.4528	$230.45	$230.45	$230.50
Purchase #6	$162.75	8.603%	$176.7514	$176.75	$176.75	$176.80
Purchase #7	$67.50	6.871%	$72.1379	$72.14	$72.15	$72.10
7 purchase totals =	$933.27		$1,023.0678	$1,023.07	$1,023.05	$1,023.20