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	$68.47	12.626%	$77.115	$77.12	$77.10	$77.10
Purchase #2	$118.48	7.150%	$126.9513	$126.95	$126.95	$127.00
Purchase #3	$48.38	12.838%	$54.591	$54.59	$54.60	$54.60
Purchase #4	$77.43	6.452%	$82.4258	$82.43	$82.45	$82.40
Purchase #5	$49.80	8.137%	$53.8522	$53.85	$53.85	$53.90
Purchase #6	$244.52	10.181%	$269.4146	$269.41	$269.40	$269.40
Purchase #7	$240.47	13.602%	$273.1787	$273.18	$273.20	$273.20
7 purchase totals =	$847.55		$937.5286	$937.53	$937.55	$937.60