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	$211.52	3.166%	$218.2167	$218.22	$218.20	$218.20
Purchase #2	$111.75	13.693%	$127.0519	$127.05	$127.05	$127.10
Purchase #3	$80.67	8.124%	$87.2236	$87.22	$87.20	$87.20
Purchase #4	$175.35	13.149%	$198.4068	$198.41	$198.40	$198.40
Purchase #5	$178.47	11.490%	$198.9762	$198.98	$199.00	$199.00
Purchase #6	$73.64	11.720%	$82.2706	$82.27	$82.25	$82.30
Purchase #7	$181.59	9.521%	$198.8792	$198.88	$198.90	$198.90
7 purchase totals =	$1,012.99		$1,111.0250	$1,111.03	$1,111.00	$1,111.10