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	$180.98	8.431%	$196.2384	$196.24	$196.25	$196.20
Purchase #2	$41.87	12.431%	$47.0749	$47.07	$47.05	$47.10
Purchase #3	$203.77	13.162%	$230.5902	$230.59	$230.60	$230.60
Purchase #4	$146.25	5.306%	$154.01	$154.01	$154.00	$154.00
Purchase #5	$106.71	4.275%	$111.2719	$111.27	$111.25	$111.30
Purchase #6	$212.41	10.192%	$234.0588	$234.06	$234.05	$234.10
Purchase #7	$102.64	7.114%	$109.9418	$109.94	$109.95	$109.90
7 purchase totals =	$994.63		$1,083.1860	$1,083.18	$1,083.15	$1,083.20