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	$223.79	3.292%	$231.1572	$231.16	$231.15	$231.20
Purchase #2	$54.72	9.459%	$59.896	$59.90	$59.90	$59.90
Purchase #3	$243.98	5.119%	$256.4693	$256.47	$256.45	$256.50
Purchase #4	$162.68	3.260%	$167.9834	$167.98	$168.00	$168.00
Purchase #5	$82.98	8.437%	$89.981	$89.98	$90.00	$90.00
Purchase #6	$230.83	4.687%	$241.649	$241.65	$241.65	$241.60
Purchase #7	$182.28	13.351%	$206.6162	$206.62	$206.60	$206.60
7 purchase totals =	$1,181.26		$1,253.7521	$1,253.76	$1,253.75	$1,253.80