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	$234.42	12.641%	$264.053	$264.05	$264.05	$264.10
Purchase #2	$24.81	13.240%	$28.0948	$28.09	$28.10	$28.10
Purchase #3	$146.64	7.835%	$158.1292	$158.13	$158.15	$158.10
Purchase #4	$145.35	10.184%	$160.1524	$160.15	$160.15	$160.20
Purchase #5	$194.88	5.724%	$206.0349	$206.03	$206.05	$206.00
Purchase #6	$59.25	11.205%	$65.889	$65.89	$65.90	$65.90
Purchase #7	$86.37	6.446%	$91.9374	$91.94	$91.95	$91.90
7 purchase totals =	$891.72		$974.2907	$974.28	$974.35	$974.30