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	$196.86	12.185%	$220.8474	$220.85	$220.85	$220.80
Purchase #2	$53.80	3.761%	$55.8234	$55.82	$55.80	$55.80
Purchase #3	$54.71	12.614%	$61.6111	$61.61	$61.60	$61.60
Purchase #4	$9.91	9.264%	$10.8281	$10.83	$10.85	$10.80
Purchase #5	$76.90	10.523%	$84.9922	$84.99	$85.00	$85.00
Purchase #6	$72.27	4.697%	$75.6645	$75.66	$75.65	$75.70
Purchase #7	$79.52	12.671%	$89.596	$89.60	$89.60	$89.60
7 purchase totals =	$543.97		$599.3627	$599.36	$599.35	$599.30