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	$61.32	8.273%	$66.393	$66.39	$66.40	$66.40
Purchase #2	$93.37	6.544%	$99.4801	$99.48	$99.50	$99.50
Purchase #3	$140.50	9.239%	$153.4808	$153.48	$153.50	$153.50
Purchase #4	$217.80	9.641%	$238.7981	$238.80	$238.80	$238.80
Purchase #5	$103.85	13.358%	$117.7223	$117.72	$117.70	$117.70
Purchase #6	$49.92	13.294%	$56.5564	$56.56	$56.55	$56.60
Purchase #7	$222.83	6.283%	$236.8304	$236.83	$236.85	$236.80
7 purchase totals =	$889.59		$969.2611	$969.26	$969.30	$969.30