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	$72.28	9.153%	$78.8958	$78.90	$78.90	$78.90
Purchase #2	$208.25	6.574%	$221.9404	$221.94	$221.95	$221.90
Purchase #3	$200.93	12.426%	$225.8976	$225.90	$225.90	$225.90
Purchase #4	$96.45	12.869%	$108.8622	$108.86	$108.85	$108.90
Purchase #5	$248.76	11.685%	$277.8276	$277.83	$277.85	$277.80
Purchase #6	$150.71	9.153%	$164.5045	$164.50	$164.50	$164.50
Purchase #7	$113.48	12.681%	$127.8704	$127.87	$127.85	$127.90
7 purchase totals =	$1,090.86		$1,205.7985	$1,205.80	$1,205.80	$1,205.80