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	$52.98	10.153%	$58.3591	$58.36	$58.35	$58.40
Purchase #2	$83.34	4.598%	$87.172	$87.17	$87.15	$87.20
Purchase #3	$235.52	8.698%	$256.0055	$256.01	$256.00	$256.00
Purchase #4	$58.77	4.801%	$61.5915	$61.59	$61.60	$61.60
Purchase #5	$84.41	6.124%	$89.5793	$89.58	$89.60	$89.60
Purchase #6	$174.79	12.601%	$196.8153	$196.82	$196.80	$196.80
Purchase #7	$231.30	9.207%	$252.5958	$252.60	$252.60	$252.60
7 purchase totals =	$921.11		$1,002.1185	$1,002.13	$1,002.10	$1,002.20