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	$205.77	9.631%	$225.5877	$225.59	$225.60	$225.60
Purchase #2	$210.51	13.357%	$238.6278	$238.63	$238.65	$238.60
Purchase #3	$169.46	3.751%	$175.8164	$175.82	$175.80	$175.80
Purchase #4	$86.38	3.765%	$89.6322	$89.63	$89.65	$89.60
Purchase #5	$234.40	5.648%	$247.6389	$247.64	$247.65	$247.60
Purchase #6	$15.56	9.120%	$16.9791	$16.98	$17.00	$17.00
Purchase #7	$124.42	12.406%	$139.8555	$139.86	$139.85	$139.90
7 purchase totals =	$1,046.50		$1,134.1376	$1,134.15	$1,134.20	$1,134.10