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	$131.85	3.523%	$136.4951	$136.50	$136.50	$136.50
Purchase #2	$176.91	4.518%	$184.9028	$184.90	$184.90	$184.90
Purchase #3	$155.32	8.569%	$168.6294	$168.63	$168.65	$168.60
Purchase #4	$177.54	5.817%	$187.8675	$187.87	$187.85	$187.90
Purchase #5	$189.30	3.478%	$195.8839	$195.88	$195.90	$195.90
Purchase #6	$61.85	10.167%	$68.1383	$68.14	$68.15	$68.10
Purchase #7	$200.52	4.127%	$208.7955	$208.80	$208.80	$208.80
7 purchase totals =	$1,093.29		$1,150.7125	$1,150.72	$1,150.75	$1,150.70