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	$221.35	5.509%	$233.5442	$233.54	$233.55	$233.50
Purchase #2	$185.45	7.482%	$199.3254	$199.33	$199.35	$199.30
Purchase #3	$94.58	6.593%	$100.8157	$100.82	$100.80	$100.80
Purchase #4	$26.27	9.601%	$28.7922	$28.79	$28.80	$28.80
Purchase #5	$128.28	11.291%	$142.7641	$142.76	$142.75	$142.80
Purchase #6	$221.32	5.382%	$233.2314	$233.23	$233.25	$233.20
Purchase #7	$231.62	7.504%	$249.0008	$249.00	$249.00	$249.00
7 purchase totals =	$1,108.87		$1,187.4738	$1,187.47	$1,187.50	$1,187.40