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	$34.85	3.359%	$36.0206	$36.02	$36.00	$36.00
Purchase #2	$146.38	3.857%	$152.0259	$152.03	$152.05	$152.00
Purchase #3	$72.33	13.367%	$81.9984	$82.00	$82.00	$82.00
Purchase #4	$35.52	3.807%	$36.8722	$36.87	$36.85	$36.90
Purchase #5	$137.80	13.754%	$156.753	$156.75	$156.75	$156.80
Purchase #6	$180.30	13.819%	$205.2157	$205.22	$205.20	$205.20
Purchase #7	$41.76	4.417%	$43.6045	$43.60	$43.60	$43.60
7 purchase totals =	$648.94		$712.4903	$712.49	$712.45	$712.50