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	$38.93	12.640%	$43.8508	$43.85	$43.85	$43.90
Purchase #2	$7.37	5.606%	$7.7832	$7.78	$7.80	$7.80
Purchase #3	$73.57	11.563%	$82.0769	$82.08	$82.10	$82.10
Purchase #4	$31.32	11.169%	$34.8181	$34.82	$34.80	$34.80
Purchase #5	$222.63	3.809%	$231.11	$231.11	$231.10	$231.10
Purchase #6	$153.26	11.315%	$170.6014	$170.60	$170.60	$170.60
Purchase #7	$222.56	12.533%	$250.4534	$250.45	$250.45	$250.50
7 purchase totals =	$749.64		$820.6938	$820.69	$820.70	$820.80