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	$46.27	4.308%	$48.2633	$48.26	$48.25	$48.30
Purchase #2	$160.94	13.397%	$182.5011	$182.50	$182.50	$182.50
Purchase #3	$203.60	9.261%	$222.4554	$222.46	$222.45	$222.50
Purchase #4	$136.91	12.234%	$153.6596	$153.66	$153.65	$153.70
Purchase #5	$42.50	13.542%	$48.2554	$48.26	$48.25	$48.30
Purchase #6	$81.92	4.482%	$85.5917	$85.59	$85.60	$85.60
Purchase #7	$95.32	3.486%	$98.6429	$98.64	$98.65	$98.60
7 purchase totals =	$767.46		$839.3694	$839.37	$839.35	$839.50