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	$106.65	5.397%	$112.4059	$112.41	$112.40	$112.40
Purchase #2	$212.31	3.378%	$219.4818	$219.48	$219.50	$219.50
Purchase #3	$90.70	13.747%	$103.1685	$103.17	$103.15	$103.20
Purchase #4	$200.92	10.199%	$221.4118	$221.41	$221.40	$221.40
Purchase #5	$142.96	4.368%	$149.2045	$149.20	$149.20	$149.20
Purchase #6	$111.61	4.391%	$116.5108	$116.51	$116.50	$116.50
Purchase #7	$122.33	12.345%	$137.4316	$137.43	$137.45	$137.40
7 purchase totals =	$987.48		$1,059.6149	$1,059.61	$1,059.60	$1,059.60