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	$147.77	7.357%	$158.6414	$158.64	$158.65	$158.60
Purchase #2	$242.45	13.840%	$276.0051	$276.01	$276.00	$276.00
Purchase #3	$216.86	6.772%	$231.5458	$231.55	$231.55	$231.50
Purchase #4	$171.29	13.375%	$194.2	$194.20	$194.20	$194.20
Purchase #5	$105.77	11.544%	$117.9801	$117.98	$118.00	$118.00
Purchase #6	$94.51	10.465%	$104.4005	$104.40	$104.40	$104.40
Purchase #7	$80.55	11.326%	$89.6731	$89.67	$89.65	$89.70
7 purchase totals =	$1,059.20		$1,172.4460	$1,172.45	$1,172.45	$1,172.40