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	$113.47	8.859%	$123.5223	$123.52	$123.50	$123.50
Purchase #2	$20.34	12.405%	$22.8632	$22.86	$22.85	$22.90
Purchase #3	$66.38	4.856%	$69.6034	$69.60	$69.60	$69.60
Purchase #4	$33.86	12.321%	$38.0319	$38.03	$38.05	$38.00
Purchase #5	$86.33	7.605%	$92.8954	$92.90	$92.90	$92.90
Purchase #6	$228.82	9.267%	$250.0247	$250.02	$250.00	$250.00
Purchase #7	$249.29	3.282%	$257.4717	$257.47	$257.45	$257.50
7 purchase totals =	$798.49		$854.4126	$854.40	$854.35	$854.40