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	$140.95	3.238%	$145.514	$145.51	$145.50	$145.50
Purchase #2	$174.39	10.804%	$193.2311	$193.23	$193.25	$193.20
Purchase #3	$211.74	10.265%	$233.4751	$233.48	$233.50	$233.50
Purchase #4	$12.39	4.436%	$12.9396	$12.94	$12.95	$12.90
Purchase #5	$22.48	10.213%	$24.7759	$24.78	$24.80	$24.80
Purchase #6	$153.59	9.527%	$168.2225	$168.22	$168.20	$168.20
Purchase #7	$193.37	3.456%	$200.0529	$200.05	$200.05	$200.10
7 purchase totals =	$908.91		$978.2111	$978.21	$978.25	$978.20