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	$67.49	7.698%	$72.6854	$72.69	$72.70	$72.70
Purchase #2	$133.75	9.367%	$146.2784	$146.28	$146.30	$146.30
Purchase #3	$70.87	3.766%	$73.539	$73.54	$73.55	$73.50
Purchase #4	$132.28	12.151%	$148.3533	$148.35	$148.35	$148.40
Purchase #5	$43.75	4.151%	$45.5661	$45.57	$45.55	$45.60
Purchase #6	$117.44	13.749%	$133.5868	$133.59	$133.60	$133.60
Purchase #7	$101.57	12.842%	$114.6136	$114.61	$114.60	$114.60
7 purchase totals =	$667.15		$734.6226	$734.63	$734.65	$734.70