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	$137.41	10.196%	$151.4203	$151.42	$151.40	$151.40
Purchase #2	$123.38	3.638%	$127.8686	$127.87	$127.85	$127.90
Purchase #3	$135.86	7.758%	$146.4	$146.40	$146.40	$146.40
Purchase #4	$204.80	3.805%	$212.5926	$212.59	$212.60	$212.60
Purchase #5	$43.49	6.545%	$46.3364	$46.34	$46.35	$46.30
Purchase #6	$45.87	5.821%	$48.5401	$48.54	$48.55	$48.50
Purchase #7	$71.90	4.218%	$74.9327	$74.93	$74.95	$74.90
7 purchase totals =	$762.71		$808.0907	$808.09	$808.10	$808.00