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	$151.43	8.147%	$163.767	$163.77	$163.75	$163.80
Purchase #2	$73.55	6.688%	$78.469	$78.47	$78.45	$78.50
Purchase #3	$125.67	9.350%	$137.4201	$137.42	$137.40	$137.40
Purchase #4	$61.37	7.368%	$65.8917	$65.89	$65.90	$65.90
Purchase #5	$59.56	9.299%	$65.0985	$65.10	$65.10	$65.10
Purchase #6	$43.61	11.277%	$48.5279	$48.53	$48.55	$48.50
Purchase #7	$60.40	8.441%	$65.4984	$65.50	$65.50	$65.50
7 purchase totals =	$575.59		$624.6726	$624.68	$624.65	$624.70