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	$175.59	10.210%	$193.5177	$193.52	$193.50	$193.50
Purchase #2	$125.89	12.849%	$142.0656	$142.07	$142.05	$142.10
Purchase #3	$59.61	13.455%	$67.6305	$67.63	$67.65	$67.60
Purchase #4	$247.65	7.561%	$266.3748	$266.37	$266.35	$266.40
Purchase #5	$79.51	13.519%	$90.259	$90.26	$90.25	$90.30
Purchase #6	$125.30	12.544%	$141.0176	$141.02	$141.00	$141.00
Purchase #7	$116.60	5.834%	$123.4024	$123.40	$123.40	$123.40
7 purchase totals =	$930.15		$1,024.2676	$1,024.27	$1,024.20	$1,024.30