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	$72.56	13.584%	$82.4166	$82.42	$82.40	$82.40
Purchase #2	$155.86	4.399%	$162.7163	$162.72	$162.70	$162.70
Purchase #3	$155.57	3.545%	$161.085	$161.09	$161.10	$161.10
Purchase #4	$94.94	3.336%	$98.1072	$98.11	$98.10	$98.10
Purchase #5	$134.53	4.731%	$140.8946	$140.89	$140.90	$140.90
Purchase #6	$138.94	13.805%	$158.1207	$158.12	$158.10	$158.10
Purchase #7	$204.57	7.665%	$220.2503	$220.25	$220.25	$220.30
7 purchase totals =	$956.97		$1,023.5907	$1,023.60	$1,023.55	$1,023.60