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	$140.53	3.225%	$145.0621	$145.06	$145.05	$145.10
Purchase #2	$155.73	7.873%	$167.9906	$167.99	$168.00	$168.00
Purchase #3	$55.37	13.714%	$62.9634	$62.96	$62.95	$63.00
Purchase #4	$185.56	7.366%	$199.2283	$199.23	$199.25	$199.20
Purchase #5	$36.25	11.842%	$40.5427	$40.54	$40.55	$40.50
Purchase #6	$166.70	7.230%	$178.7524	$178.75	$178.75	$178.80
Purchase #7	$59.89	10.710%	$66.3042	$66.30	$66.30	$66.30
7 purchase totals =	$800.03		$860.8437	$860.83	$860.85	$860.90