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	$232.39	12.563%	$261.5852	$261.59	$261.60	$261.60
Purchase #2	$28.52	8.376%	$30.9088	$30.91	$30.90	$30.90
Purchase #3	$105.46	6.379%	$112.1873	$112.19	$112.20	$112.20
Purchase #4	$239.42	13.295%	$271.2509	$271.25	$271.25	$271.30
Purchase #5	$180.71	9.755%	$198.3383	$198.34	$198.35	$198.30
Purchase #6	$93.53	10.758%	$103.592	$103.59	$103.60	$103.60
Purchase #7	$74.85	12.190%	$83.9742	$83.97	$83.95	$84.00
7 purchase totals =	$954.88		$1,061.8367	$1,061.84	$1,061.85	$1,061.90