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	$102.63	11.313%	$114.2405	$114.24	$114.25	$114.20
Purchase #2	$50.81	4.487%	$53.0898	$53.09	$53.10	$53.10
Purchase #3	$72.40	11.536%	$80.7521	$80.75	$80.75	$80.80
Purchase #4	$7.58	13.137%	$8.5758	$8.58	$8.60	$8.60
Purchase #5	$196.59	6.636%	$209.6357	$209.64	$209.65	$209.60
Purchase #6	$222.60	7.323%	$238.901	$238.90	$238.90	$238.90
Purchase #7	$211.28	5.134%	$222.1271	$222.13	$222.15	$222.10
7 purchase totals =	$863.89		$927.3220	$927.33	$927.40	$927.30