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	$142.62	5.352%	$150.253	$150.25	$150.25	$150.30
Purchase #2	$134.61	7.704%	$144.9804	$144.98	$145.00	$145.00
Purchase #3	$100.30	8.807%	$109.1334	$109.13	$109.15	$109.10
Purchase #4	$48.59	5.611%	$51.3164	$51.32	$51.30	$51.30
Purchase #5	$167.54	4.667%	$175.3591	$175.36	$175.35	$175.40
Purchase #6	$40.78	5.509%	$43.0266	$43.03	$43.05	$43.00
Purchase #7	$174.65	12.272%	$196.083	$196.08	$196.10	$196.10
7 purchase totals =	$809.09		$870.1519	$870.15	$870.20	$870.20