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	$211.29	9.254%	$230.8428	$230.84	$230.85	$230.80
Purchase #2	$241.71	9.263%	$264.0996	$264.10	$264.10	$264.10
Purchase #3	$178.57	12.255%	$200.4538	$200.45	$200.45	$200.50
Purchase #4	$186.34	10.683%	$206.2467	$206.25	$206.25	$206.20
Purchase #5	$125.72	13.658%	$142.8908	$142.89	$142.90	$142.90
Purchase #6	$36.71	5.168%	$38.6072	$38.61	$38.60	$38.60
Purchase #7	$106.27	6.499%	$113.1765	$113.18	$113.20	$113.20
7 purchase totals =	$1,086.61		$1,196.3174	$1,196.32	$1,196.35	$1,196.30