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	$139.87	8.696%	$152.0331	$152.03	$152.05	$152.00
Purchase #2	$247.79	4.295%	$258.4326	$258.43	$258.45	$258.40
Purchase #3	$129.31	10.264%	$142.5824	$142.58	$142.60	$142.60
Purchase #4	$111.54	4.523%	$116.585	$116.59	$116.60	$116.60
Purchase #5	$6.93	5.546%	$7.3143	$7.31	$7.30	$7.30
Purchase #6	$79.65	8.311%	$86.2697	$86.27	$86.25	$86.30
Purchase #7	$93.50	3.536%	$96.8062	$96.81	$96.80	$96.80
7 purchase totals =	$808.59		$860.0233	$860.02	$860.05	$860.00