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	$202.32	10.635%	$223.8367	$223.84	$223.85	$223.80
Purchase #2	$140.40	5.616%	$148.2849	$148.28	$148.30	$148.30
Purchase #3	$216.43	3.332%	$223.6414	$223.64	$223.65	$223.60
Purchase #4	$166.51	10.865%	$184.6013	$184.60	$184.60	$184.60
Purchase #5	$77.39	4.205%	$80.6442	$80.64	$80.65	$80.60
Purchase #6	$162.52	3.685%	$168.5089	$168.51	$168.50	$168.50
Purchase #7	$206.85	9.726%	$226.9682	$226.97	$226.95	$227.00
7 purchase totals =	$1,172.42		$1,256.4856	$1,256.48	$1,256.50	$1,256.40