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	$52.87	12.646%	$59.5559	$59.56	$59.55	$59.60
Purchase #2	$13.49	9.725%	$14.8019	$14.80	$14.80	$14.80
Purchase #3	$207.40	3.767%	$215.2128	$215.21	$215.20	$215.20
Purchase #4	$242.42	12.417%	$272.5213	$272.52	$272.50	$272.50
Purchase #5	$154.39	8.331%	$167.2522	$167.25	$167.25	$167.30
Purchase #6	$165.83	7.683%	$178.5707	$178.57	$178.55	$178.60
Purchase #7	$88.61	6.629%	$94.484	$94.48	$94.50	$94.50
7 purchase totals =	$925.01		$1,002.3988	$1,002.39	$1,002.35	$1,002.50