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	$57.43	11.815%	$64.2154	$64.22	$64.20	$64.20
Purchase #2	$33.47	9.552%	$36.6671	$36.67	$36.65	$36.70
Purchase #3	$13.42	8.540%	$14.5661	$14.57	$14.55	$14.60
Purchase #4	$50.90	10.475%	$56.2318	$56.23	$56.25	$56.20
Purchase #5	$157.27	7.111%	$168.4535	$168.45	$168.45	$168.50
Purchase #6	$170.83	9.652%	$187.3185	$187.32	$187.30	$187.30
Purchase #7	$164.39	12.825%	$185.473	$185.47	$185.45	$185.50
7 purchase totals =	$647.71		$712.9254	$712.93	$712.85	$713.00