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	$99.29	12.431%	$111.6327	$111.63	$111.65	$111.60
Purchase #2	$18.59	13.224%	$21.0483	$21.05	$21.05	$21.00
Purchase #3	$74.29	7.527%	$79.8818	$79.88	$79.90	$79.90
Purchase #4	$200.65	4.318%	$209.3141	$209.31	$209.30	$209.30
Purchase #5	$207.37	5.391%	$218.5493	$218.55	$218.55	$218.50
Purchase #6	$154.50	5.158%	$162.4691	$162.47	$162.45	$162.50
Purchase #7	$150.25	4.260%	$156.6507	$156.65	$156.65	$156.70
7 purchase totals =	$904.94		$959.5460	$959.54	$959.55	$959.50