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	$93.66	3.338%	$96.7864	$96.79	$96.80	$96.80
Purchase #2	$245.31	10.771%	$271.7323	$271.73	$271.75	$271.70
Purchase #3	$38.84	12.472%	$43.6841	$43.68	$43.70	$43.70
Purchase #4	$242.61	7.829%	$261.6039	$261.60	$261.60	$261.60
Purchase #5	$36.85	13.245%	$41.7308	$41.73	$41.75	$41.70
Purchase #6	$169.56	12.144%	$190.1514	$190.15	$190.15	$190.20
Purchase #7	$138.61	11.721%	$154.8565	$154.86	$154.85	$154.90
7 purchase totals =	$965.44		$1,060.5454	$1,060.54	$1,060.60	$1,060.60