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	$70.38	3.552%	$72.8799	$72.88	$72.90	$72.90
Purchase #2	$229.92	4.862%	$241.0987	$241.10	$241.10	$241.10
Purchase #3	$199.56	4.229%	$207.9994	$208.00	$208.00	$208.00
Purchase #4	$188.28	10.856%	$208.7197	$208.72	$208.70	$208.70
Purchase #5	$214.53	3.690%	$222.4462	$222.45	$222.45	$222.40
Purchase #6	$116.94	5.490%	$123.36	$123.36	$123.35	$123.40
Purchase #7	$108.70	12.584%	$122.3788	$122.38	$122.40	$122.40
7 purchase totals =	$1,128.31		$1,198.8827	$1,198.89	$1,198.90	$1,198.90