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	$150.74	9.109%	$164.4709	$164.47	$164.45	$164.50
Purchase #2	$149.28	13.611%	$169.5985	$169.60	$169.60	$169.60
Purchase #3	$44.78	11.384%	$49.8778	$49.88	$49.90	$49.90
Purchase #4	$197.87	12.521%	$222.6453	$222.65	$222.65	$222.60
Purchase #5	$45.83	6.457%	$48.7892	$48.79	$48.80	$48.80
Purchase #6	$232.32	7.577%	$249.9229	$249.92	$249.90	$249.90
Purchase #7	$113.42	12.516%	$127.6156	$127.62	$127.60	$127.60
7 purchase totals =	$934.24		$1,032.9202	$1,032.93	$1,032.90	$1,032.90