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	$135.61	6.354%	$144.2267	$144.23	$144.25	$144.20
Purchase #2	$245.92	13.102%	$278.1404	$278.14	$278.15	$278.10
Purchase #3	$233.85	3.175%	$241.2747	$241.27	$241.25	$241.30
Purchase #4	$48.39	3.601%	$50.1325	$50.13	$50.15	$50.10
Purchase #5	$77.25	12.584%	$86.9711	$86.97	$86.95	$87.00
Purchase #6	$221.96	8.547%	$240.9309	$240.93	$240.95	$240.90
Purchase #7	$148.92	3.768%	$154.5313	$154.53	$154.55	$154.50
7 purchase totals =	$1,111.90		$1,196.2076	$1,196.20	$1,196.25	$1,196.10