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	$175.90	3.760%	$182.5138	$182.51	$182.50	$182.50
Purchase #2	$232.65	10.225%	$256.4385	$256.44	$256.45	$256.40
Purchase #3	$82.99	3.412%	$85.8216	$85.82	$85.80	$85.80
Purchase #4	$126.70	12.646%	$142.7225	$142.72	$142.70	$142.70
Purchase #5	$132.89	12.616%	$149.6554	$149.66	$149.65	$149.70
Purchase #6	$238.61	7.483%	$256.4652	$256.47	$256.45	$256.50
Purchase #7	$45.27	9.208%	$49.4385	$49.44	$49.45	$49.40
7 purchase totals =	$1,035.01		$1,123.0555	$1,123.06	$1,123.00	$1,123.00