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	$131.82	6.170%	$139.9533	$139.95	$139.95	$140.00
Purchase #2	$77.66	9.652%	$85.1557	$85.16	$85.15	$85.20
Purchase #3	$108.64	5.285%	$114.3816	$114.38	$114.40	$114.40
Purchase #4	$92.38	5.509%	$97.4692	$97.47	$97.45	$97.50
Purchase #5	$65.32	9.468%	$71.5045	$71.50	$71.50	$71.50
Purchase #6	$168.70	3.416%	$174.4628	$174.46	$174.45	$174.50
Purchase #7	$59.25	10.181%	$65.2822	$65.28	$65.30	$65.30
7 purchase totals =	$703.77		$748.2093	$748.20	$748.20	$748.40