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	$72.88	13.359%	$82.616	$82.62	$82.60	$82.60
Purchase #2	$103.35	10.110%	$113.7987	$113.80	$113.80	$113.80
Purchase #3	$180.57	9.108%	$197.0163	$197.02	$197.00	$197.00
Purchase #4	$137.30	5.539%	$144.905	$144.91	$144.90	$144.90
Purchase #5	$194.78	7.233%	$208.8684	$208.87	$208.85	$208.90
Purchase #6	$91.56	13.613%	$104.0241	$104.02	$104.00	$104.00
Purchase #7	$145.64	4.746%	$152.5521	$152.55	$152.55	$152.60
7 purchase totals =	$926.08		$1,003.7806	$1,003.79	$1,003.70	$1,003.80