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	$59.78	5.529%	$63.0852	$63.09	$63.10	$63.10
Purchase #2	$93.76	8.797%	$102.0081	$102.01	$102.00	$102.00
Purchase #3	$185.95	7.218%	$199.3719	$199.37	$199.35	$199.40
Purchase #4	$100.74	10.368%	$111.1847	$111.18	$111.20	$111.20
Purchase #5	$65.96	10.467%	$72.864	$72.86	$72.85	$72.90
Purchase #6	$191.99	10.671%	$212.4773	$212.48	$212.50	$212.50
Purchase #7	$6.75	7.123%	$7.2308	$7.23	$7.25	$7.20
7 purchase totals =	$704.93		$768.2220	$768.22	$768.25	$768.30