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	$169.60	7.816%	$182.8559	$182.86	$182.85	$182.90
Purchase #2	$11.39	4.361%	$11.8867	$11.89	$11.90	$11.90
Purchase #3	$23.27	6.407%	$24.7609	$24.76	$24.75	$24.80
Purchase #4	$57.45	12.300%	$64.5164	$64.52	$64.50	$64.50
Purchase #5	$9.88	10.261%	$10.8938	$10.89	$10.90	$10.90
Purchase #6	$17.62	5.583%	$18.6037	$18.60	$18.60	$18.60
Purchase #7	$5.89	9.145%	$6.4286	$6.43	$6.45	$6.40
7 purchase totals =	$295.10		$319.9460	$319.95	$319.95	$320.00