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	$50.59	3.309%	$52.264	$52.26	$52.25	$52.30
Purchase #2	$84.74	3.514%	$87.7178	$87.72	$87.70	$87.70
Purchase #3	$88.83	3.597%	$92.0252	$92.03	$92.05	$92.00
Purchase #4	$247.86	10.389%	$273.6102	$273.61	$273.60	$273.60
Purchase #5	$117.55	10.282%	$129.6365	$129.64	$129.65	$129.60
Purchase #6	$100.93	12.340%	$113.3848	$113.38	$113.40	$113.40
Purchase #7	$105.96	5.339%	$111.6172	$111.62	$111.60	$111.60
7 purchase totals =	$796.46		$860.2557	$860.26	$860.25	$860.20