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	$102.42	10.861%	$113.5438	$113.54	$113.55	$113.50
Purchase #2	$70.69	10.354%	$78.0092	$78.01	$78.00	$78.00
Purchase #3	$156.54	12.116%	$175.5064	$175.51	$175.50	$175.50
Purchase #4	$17.28	3.826%	$17.9411	$17.94	$17.95	$17.90
Purchase #5	$218.64	6.679%	$233.243	$233.24	$233.25	$233.20
Purchase #6	$109.44	13.557%	$124.2768	$124.28	$124.30	$124.30
Purchase #7	$46.82	10.521%	$51.7459	$51.75	$51.75	$51.70
7 purchase totals =	$721.83		$794.2662	$794.27	$794.30	$794.10