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	$249.90	5.578%	$263.8394	$263.84	$263.85	$263.80
Purchase #2	$172.28	13.775%	$196.0116	$196.01	$196.00	$196.00
Purchase #3	$135.41	6.537%	$144.2618	$144.26	$144.25	$144.30
Purchase #4	$11.49	11.584%	$12.821	$12.82	$12.80	$12.80
Purchase #5	$65.42	10.461%	$72.2636	$72.26	$72.25	$72.30
Purchase #6	$137.55	12.444%	$154.6667	$154.67	$154.65	$154.70
Purchase #7	$208.57	11.869%	$233.3252	$233.33	$233.35	$233.30
7 purchase totals =	$980.62		$1,077.1893	$1,077.19	$1,077.15	$1,077.20