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	$80.85	3.140%	$83.3887	$83.39	$83.40	$83.40
Purchase #2	$95.99	10.361%	$105.9355	$105.94	$105.95	$105.90
Purchase #3	$179.92	9.106%	$196.3035	$196.30	$196.30	$196.30
Purchase #4	$166.77	7.292%	$178.9309	$178.93	$178.95	$178.90
Purchase #5	$175.54	8.671%	$190.7611	$190.76	$190.75	$190.80
Purchase #6	$22.57	9.681%	$24.755	$24.76	$24.75	$24.80
Purchase #7	$234.42	4.415%	$244.7696	$244.77	$244.75	$244.80
7 purchase totals =	$956.06		$1,024.8443	$1,024.85	$1,024.85	$1,024.90