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	$109.68	9.298%	$119.878	$119.88	$119.90	$119.90
Purchase #2	$233.33	8.471%	$253.0954	$253.10	$253.10	$253.10
Purchase #3	$67.67	7.298%	$72.6086	$72.61	$72.60	$72.60
Purchase #4	$135.97	6.143%	$144.3226	$144.32	$144.30	$144.30
Purchase #5	$40.94	8.233%	$44.3106	$44.31	$44.30	$44.30
Purchase #6	$204.56	4.815%	$214.4096	$214.41	$214.40	$214.40
Purchase #7	$123.46	3.159%	$127.3601	$127.36	$127.35	$127.40
7 purchase totals =	$915.61		$975.9849	$975.99	$975.95	$976.00