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	$69.67	4.314%	$72.6756	$72.68	$72.70	$72.70
Purchase #2	$111.39	9.230%	$121.6713	$121.67	$121.65	$121.70
Purchase #3	$192.98	6.542%	$205.6048	$205.60	$205.60	$205.60
Purchase #4	$134.91	3.856%	$140.1121	$140.11	$140.10	$140.10
Purchase #5	$156.99	7.314%	$168.4722	$168.47	$168.45	$168.50
Purchase #6	$66.83	8.632%	$72.5988	$72.60	$72.60	$72.60
Purchase #7	$94.91	4.789%	$99.4552	$99.46	$99.45	$99.50
7 purchase totals =	$827.68		$880.5900	$880.59	$880.55	$880.70