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	$86.31	12.818%	$97.3732	$97.37	$97.35	$97.40
Purchase #2	$238.90	12.859%	$269.6202	$269.62	$269.60	$269.60
Purchase #3	$159.40	11.410%	$177.5875	$177.59	$177.60	$177.60
Purchase #4	$85.28	5.337%	$89.8314	$89.83	$89.85	$89.80
Purchase #5	$90.90	9.509%	$99.5437	$99.54	$99.55	$99.50
Purchase #6	$180.61	12.845%	$203.8094	$203.81	$203.80	$203.80
Purchase #7	$114.51	8.458%	$124.1953	$124.20	$124.20	$124.20
7 purchase totals =	$955.91		$1,061.9607	$1,061.96	$1,061.95	$1,061.90