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	$76.52	12.851%	$86.3536	$86.35	$86.35	$86.40
Purchase #2	$36.92	11.276%	$41.0831	$41.08	$41.10	$41.10
Purchase #3	$77.63	5.764%	$82.1046	$82.10	$82.10	$82.10
Purchase #4	$177.74	10.611%	$196.6	$196.60	$196.60	$196.60
Purchase #5	$241.65	5.366%	$254.6169	$254.62	$254.60	$254.60
Purchase #6	$179.92	7.766%	$193.8926	$193.89	$193.90	$193.90
Purchase #7	$89.67	12.445%	$100.8294	$100.83	$100.85	$100.80
7 purchase totals =	$880.05		$955.4802	$955.47	$955.50	$955.50