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	$77.96	5.699%	$82.4029	$82.40	$82.40	$82.40
Purchase #2	$103.37	5.430%	$108.983	$108.98	$109.00	$109.00
Purchase #3	$221.84	5.185%	$233.3424	$233.34	$233.35	$233.30
Purchase #4	$148.88	3.182%	$153.6174	$153.62	$153.60	$153.60
Purchase #5	$106.46	4.240%	$110.9739	$110.97	$110.95	$111.00
Purchase #6	$88.60	4.787%	$92.8413	$92.84	$92.85	$92.80
Purchase #7	$112.50	9.780%	$123.5025	$123.50	$123.50	$123.50
7 purchase totals =	$859.61		$905.6634	$905.65	$905.65	$905.60