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	$60.25	7.229%	$64.6055	$64.61	$64.60	$64.60
Purchase #2	$116.58	3.219%	$120.3327	$120.33	$120.35	$120.30
Purchase #3	$129.90	13.631%	$147.6067	$147.61	$147.60	$147.60
Purchase #4	$76.56	11.587%	$85.431	$85.43	$85.45	$85.40
Purchase #5	$133.99	5.426%	$141.2603	$141.26	$141.25	$141.30
Purchase #6	$10.45	9.525%	$11.4454	$11.45	$11.45	$11.40
Purchase #7	$24.82	10.412%	$27.4043	$27.40	$27.40	$27.40
7 purchase totals =	$552.55		$598.0859	$598.09	$598.10	$598.00