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	$245.80	9.702%	$269.6475	$269.65	$269.65	$269.60
Purchase #2	$149.92	13.561%	$170.2507	$170.25	$170.25	$170.30
Purchase #3	$35.58	6.294%	$37.8194	$37.82	$37.80	$37.80
Purchase #4	$59.50	3.306%	$61.4671	$61.47	$61.45	$61.50
Purchase #5	$211.89	10.392%	$233.9096	$233.91	$233.90	$233.90
Purchase #6	$142.42	10.375%	$157.1961	$157.20	$157.20	$157.20
Purchase #7	$120.79	5.827%	$127.8284	$127.83	$127.85	$127.80
7 purchase totals =	$965.90		$1,058.1188	$1,058.13	$1,058.10	$1,058.10