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	$73.34	12.294%	$82.3564	$82.36	$82.35	$82.40
Purchase #2	$175.38	10.680%	$194.1106	$194.11	$194.10	$194.10
Purchase #3	$20.50	7.593%	$22.0566	$22.06	$22.05	$22.10
Purchase #4	$65.94	9.750%	$72.3692	$72.37	$72.35	$72.40
Purchase #5	$147.74	3.789%	$153.3379	$153.34	$153.35	$153.30
Purchase #6	$105.98	5.163%	$111.4517	$111.45	$111.45	$111.50
Purchase #7	$82.46	5.803%	$87.2452	$87.25	$87.25	$87.20
7 purchase totals =	$671.34		$722.9276	$722.94	$722.90	$723.00