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	$47.53	10.862%	$52.6927	$52.69	$52.70	$52.70
Purchase #2	$21.41	3.600%	$22.1808	$22.18	$22.20	$22.20
Purchase #3	$195.47	8.127%	$211.3558	$211.36	$211.35	$211.40
Purchase #4	$158.26	5.281%	$166.6177	$166.62	$166.60	$166.60
Purchase #5	$200.36	10.434%	$221.2656	$221.27	$221.25	$221.30
Purchase #6	$113.83	12.387%	$127.9301	$127.93	$127.95	$127.90
Purchase #7	$52.90	12.553%	$59.5405	$59.54	$59.55	$59.50
7 purchase totals =	$789.76		$861.5832	$861.59	$861.60	$861.60