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	$67.66	5.534%	$71.4043	$71.40	$71.40	$71.40
Purchase #2	$31.68	12.366%	$35.5975	$35.60	$35.60	$35.60
Purchase #3	$125.69	11.572%	$140.2348	$140.23	$140.25	$140.20
Purchase #4	$33.42	9.856%	$36.7139	$36.71	$36.70	$36.70
Purchase #5	$244.31	12.854%	$275.7136	$275.71	$275.70	$275.70
Purchase #6	$39.80	8.346%	$43.1217	$43.12	$43.10	$43.10
Purchase #7	$75.86	8.611%	$82.3923	$82.39	$82.40	$82.40
7 purchase totals =	$618.42		$685.1781	$685.16	$685.15	$685.10