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	$65.38	4.680%	$68.4398	$68.44	$68.45	$68.40
Purchase #2	$243.71	4.555%	$254.811	$254.81	$254.80	$254.80
Purchase #3	$118.35	11.185%	$131.5874	$131.59	$131.60	$131.60
Purchase #4	$231.47	12.519%	$260.4477	$260.45	$260.45	$260.40
Purchase #5	$101.81	6.111%	$108.0316	$108.03	$108.05	$108.00
Purchase #6	$74.26	11.154%	$82.543	$82.54	$82.55	$82.50
Purchase #7	$131.29	6.542%	$139.879	$139.88	$139.90	$139.90
7 purchase totals =	$966.27		$1,045.7395	$1,045.74	$1,045.80	$1,045.60