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	$87.56	7.236%	$93.8958	$93.90	$93.90	$93.90
Purchase #2	$78.59	13.328%	$89.0645	$89.06	$89.05	$89.10
Purchase #3	$47.46	13.128%	$53.6905	$53.69	$53.70	$53.70
Purchase #4	$59.98	9.696%	$65.7957	$65.80	$65.80	$65.80
Purchase #5	$114.56	3.742%	$118.8468	$118.85	$118.85	$118.80
Purchase #6	$45.38	5.357%	$47.811	$47.81	$47.80	$47.80
Purchase #7	$63.25	5.387%	$66.6573	$66.66	$66.65	$66.70
7 purchase totals =	$496.78		$535.7616	$535.77	$535.75	$535.80