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	$235.45	5.562%	$248.5457	$248.55	$248.55	$248.50
Purchase #2	$35.80	7.187%	$38.3729	$38.37	$38.35	$38.40
Purchase #3	$153.95	8.790%	$167.4822	$167.48	$167.50	$167.50
Purchase #4	$143.40	5.665%	$151.5236	$151.52	$151.50	$151.50
Purchase #5	$81.38	6.426%	$86.6095	$86.61	$86.60	$86.60
Purchase #6	$144.42	6.670%	$154.0528	$154.05	$154.05	$154.10
Purchase #7	$160.35	4.290%	$167.229	$167.23	$167.25	$167.20
7 purchase totals =	$954.75		$1,013.8157	$1,013.81	$1,013.80	$1,013.80