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	$116.90	12.393%	$131.3874	$131.39	$131.40	$131.40
Purchase #2	$54.37	13.244%	$61.5708	$61.57	$61.55	$61.60
Purchase #3	$75.45	6.444%	$80.312	$80.31	$80.30	$80.30
Purchase #4	$126.68	5.503%	$133.6512	$133.65	$133.65	$133.70
Purchase #5	$169.87	12.602%	$191.277	$191.28	$191.30	$191.30
Purchase #6	$210.30	3.298%	$217.2357	$217.24	$217.25	$217.20
Purchase #7	$210.57	13.274%	$238.5211	$238.52	$238.50	$238.50
7 purchase totals =	$964.14		$1,053.9552	$1,053.96	$1,053.95	$1,054.00