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	$54.76	12.265%	$61.4763	$61.48	$61.50	$61.50
Purchase #2	$65.51	13.515%	$74.3637	$74.36	$74.35	$74.40
Purchase #3	$205.52	10.254%	$226.594	$226.59	$226.60	$226.60
Purchase #4	$244.41	11.601%	$272.764	$272.76	$272.75	$272.80
Purchase #5	$5.31	5.630%	$5.609	$5.61	$5.60	$5.60
Purchase #6	$48.92	9.231%	$53.4358	$53.44	$53.45	$53.40
Purchase #7	$87.90	3.264%	$90.7691	$90.77	$90.75	$90.80
7 purchase totals =	$712.33		$785.0119	$785.01	$785.00	$785.10