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	$117.92	8.513%	$127.9585	$127.96	$127.95	$128.00
Purchase #2	$238.96	12.587%	$269.0379	$269.04	$269.05	$269.00
Purchase #3	$249.50	3.653%	$258.6142	$258.61	$258.60	$258.60
Purchase #4	$245.43	12.671%	$276.5284	$276.53	$276.55	$276.50
Purchase #5	$188.40	4.494%	$196.8667	$196.87	$196.85	$196.90
Purchase #6	$205.71	8.235%	$222.6502	$222.65	$222.65	$222.70
Purchase #7	$231.65	8.620%	$251.6182	$251.62	$251.60	$251.60
7 purchase totals =	$1,477.57		$1,603.2741	$1,603.28	$1,603.25	$1,603.30