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	$138.78	10.108%	$152.8079	$152.81	$152.80	$152.80
Purchase #2	$196.43	8.224%	$212.5844	$212.58	$212.60	$212.60
Purchase #3	$164.58	8.734%	$178.9544	$178.95	$178.95	$179.00
Purchase #4	$141.86	10.154%	$156.2645	$156.26	$156.25	$156.30
Purchase #5	$198.43	12.613%	$223.458	$223.46	$223.45	$223.50
Purchase #6	$239.38	7.475%	$257.2737	$257.27	$257.25	$257.30
Purchase #7	$122.71	6.761%	$131.0064	$131.01	$131.00	$131.00
7 purchase totals =	$1,202.17		$1,312.3493	$1,312.34	$1,312.30	$1,312.50