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	$59.65	8.281%	$64.5896	$64.59	$64.60	$64.60
Purchase #2	$138.55	5.730%	$146.4889	$146.49	$146.50	$146.50
Purchase #3	$103.88	4.671%	$108.7322	$108.73	$108.75	$108.70
Purchase #4	$250.66	12.478%	$281.9374	$281.94	$281.95	$281.90
Purchase #5	$134.66	13.459%	$152.7839	$152.78	$152.80	$152.80
Purchase #6	$152.38	12.678%	$171.6987	$171.70	$171.70	$171.70
Purchase #7	$194.95	11.321%	$217.0203	$217.02	$217.00	$217.00
7 purchase totals =	$1,034.73		$1,143.2510	$1,143.25	$1,143.30	$1,143.20