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	$155.57	10.286%	$171.5719	$171.57	$171.55	$171.60
Purchase #2	$232.90	3.720%	$241.5639	$241.56	$241.55	$241.60
Purchase #3	$189.67	3.382%	$196.0846	$196.08	$196.10	$196.10
Purchase #4	$195.34	6.797%	$208.6173	$208.62	$208.60	$208.60
Purchase #5	$163.50	5.706%	$172.8293	$172.83	$172.85	$172.80
Purchase #6	$238.43	7.427%	$256.1382	$256.14	$256.15	$256.10
Purchase #7	$163.85	13.408%	$185.819	$185.82	$185.80	$185.80
7 purchase totals =	$1,339.26		$1,432.6242	$1,432.62	$1,432.60	$1,432.60