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	$85.78	12.225%	$96.2666	$96.27	$96.25	$96.30
Purchase #2	$206.59	7.647%	$222.3879	$222.39	$222.40	$222.40
Purchase #3	$51.83	5.166%	$54.5075	$54.51	$54.50	$54.50
Purchase #4	$178.34	11.610%	$199.0453	$199.05	$199.05	$199.00
Purchase #5	$111.73	9.810%	$122.6907	$122.69	$122.70	$122.70
Purchase #6	$210.37	4.726%	$220.3121	$220.31	$220.30	$220.30
Purchase #7	$82.91	10.247%	$91.4058	$91.41	$91.40	$91.40
7 purchase totals =	$927.55		$1,006.6159	$1,006.63	$1,006.60	$1,006.60