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	$129.93	7.648%	$139.867	$139.87	$139.85	$139.90
Purchase #2	$166.26	12.859%	$187.6394	$187.64	$187.65	$187.60
Purchase #3	$104.42	11.401%	$116.3249	$116.32	$116.30	$116.30
Purchase #4	$55.60	10.244%	$61.2957	$61.30	$61.30	$61.30
Purchase #5	$147.36	5.582%	$155.5856	$155.59	$155.60	$155.60
Purchase #6	$170.39	4.208%	$177.56	$177.56	$177.55	$177.60
Purchase #7	$35.50	6.631%	$37.854	$37.85	$37.85	$37.90
7 purchase totals =	$809.46		$876.1266	$876.13	$876.10	$876.20