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	$78.43	9.874%	$86.1742	$86.17	$86.15	$86.20
Purchase #2	$65.81	10.396%	$72.6516	$72.65	$72.65	$72.70
Purchase #3	$240.91	7.221%	$258.3061	$258.31	$258.30	$258.30
Purchase #4	$234.88	3.211%	$242.422	$242.42	$242.40	$242.40
Purchase #5	$111.53	4.582%	$116.6403	$116.64	$116.65	$116.60
Purchase #6	$210.75	8.272%	$228.1832	$228.18	$228.20	$228.20
Purchase #7	$51.44	10.772%	$56.9811	$56.98	$57.00	$57.00
7 purchase totals =	$993.75		$1,061.3585	$1,061.35	$1,061.35	$1,061.40