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	$206.33	9.431%	$225.789	$225.79	$225.80	$225.80
Purchase #2	$156.94	10.203%	$172.9526	$172.95	$172.95	$173.00
Purchase #3	$242.54	3.701%	$251.5164	$251.52	$251.50	$251.50
Purchase #4	$44.25	7.109%	$47.3957	$47.40	$47.40	$47.40
Purchase #5	$55.51	10.396%	$61.2808	$61.28	$61.30	$61.30
Purchase #6	$63.77	13.402%	$72.3165	$72.32	$72.30	$72.30
Purchase #7	$29.91	6.281%	$31.7886	$31.79	$31.80	$31.80
7 purchase totals =	$799.25		$863.0396	$863.05	$863.05	$863.10