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	$241.35	10.345%	$266.3177	$266.32	$266.30	$266.30
Purchase #2	$22.32	11.321%	$24.8468	$24.85	$24.85	$24.80
Purchase #3	$98.82	13.715%	$112.3732	$112.37	$112.35	$112.40
Purchase #4	$141.91	12.397%	$159.5026	$159.50	$159.50	$159.50
Purchase #5	$142.62	5.326%	$150.2159	$150.22	$150.20	$150.20
Purchase #6	$72.73	5.694%	$76.8712	$76.87	$76.85	$76.90
Purchase #7	$241.97	9.730%	$265.5137	$265.51	$265.50	$265.50
7 purchase totals =	$961.72		$1,055.6411	$1,055.64	$1,055.55	$1,055.60