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	$108.59	7.562%	$116.8016	$116.80	$116.80	$116.80
Purchase #2	$114.69	7.771%	$123.6026	$123.60	$123.60	$123.60
Purchase #3	$154.47	8.529%	$167.6447	$167.64	$167.65	$167.60
Purchase #4	$133.44	13.273%	$151.1515	$151.15	$151.15	$151.20
Purchase #5	$224.37	8.445%	$243.318	$243.32	$243.30	$243.30
Purchase #6	$32.67	10.405%	$36.0693	$36.07	$36.05	$36.10
Purchase #7	$37.55	12.569%	$42.2697	$42.27	$42.25	$42.30
7 purchase totals =	$805.78		$880.8574	$880.85	$880.80	$880.90