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	$105.44	10.792%	$116.8191	$116.82	$116.80	$116.80
Purchase #2	$233.76	9.538%	$256.056	$256.06	$256.05	$256.10
Purchase #3	$168.53	4.746%	$176.5284	$176.53	$176.55	$176.50
Purchase #4	$208.93	9.737%	$229.2735	$229.27	$229.25	$229.30
Purchase #5	$131.27	4.325%	$136.9474	$136.95	$136.95	$136.90
Purchase #6	$98.43	4.310%	$102.6723	$102.67	$102.65	$102.70
Purchase #7	$81.99	10.187%	$90.3423	$90.34	$90.35	$90.30
7 purchase totals =	$1,028.35		$1,108.6390	$1,108.64	$1,108.60	$1,108.60