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	$188.79	12.873%	$213.0929	$213.09	$213.10	$213.10
Purchase #2	$127.77	10.865%	$141.6522	$141.65	$141.65	$141.70
Purchase #3	$115.83	9.294%	$126.5952	$126.60	$126.60	$126.60
Purchase #4	$17.45	13.305%	$19.7717	$19.77	$19.75	$19.80
Purchase #5	$177.83	10.489%	$196.4826	$196.48	$196.50	$196.50
Purchase #6	$105.47	9.772%	$115.7765	$115.78	$115.80	$115.80
Purchase #7	$240.37	13.826%	$273.6036	$273.60	$273.60	$273.60
7 purchase totals =	$973.51		$1,086.9747	$1,086.97	$1,087.00	$1,087.10