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	$67.95	7.810%	$73.2569	$73.26	$73.25	$73.30
Purchase #2	$86.31	5.232%	$90.8257	$90.83	$90.85	$90.80
Purchase #3	$189.64	12.855%	$214.0182	$214.02	$214.00	$214.00
Purchase #4	$79.65	12.448%	$89.5648	$89.56	$89.55	$89.60
Purchase #5	$204.97	4.714%	$214.6323	$214.63	$214.65	$214.60
Purchase #6	$241.88	12.253%	$271.5176	$271.52	$271.50	$271.50
Purchase #7	$93.53	7.792%	$100.8179	$100.82	$100.80	$100.80
7 purchase totals =	$963.93		$1,054.6334	$1,054.64	$1,054.60	$1,054.60