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	$52.71	12.478%	$59.2872	$59.29	$59.30	$59.30
Purchase #2	$84.44	12.599%	$95.0786	$95.08	$95.10	$95.10
Purchase #3	$240.69	3.581%	$249.3091	$249.31	$249.30	$249.30
Purchase #4	$157.93	13.523%	$179.2869	$179.29	$179.30	$179.30
Purchase #5	$69.26	12.552%	$77.9535	$77.95	$77.95	$78.00
Purchase #6	$13.83	7.723%	$14.8981	$14.90	$14.90	$14.90
Purchase #7	$113.52	11.716%	$126.82	$126.82	$126.80	$126.80
7 purchase totals =	$732.38		$802.6334	$802.64	$802.65	$802.70