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	$117.64	5.301%	$123.8761	$123.88	$123.90	$123.90
Purchase #2	$11.65	13.302%	$13.1997	$13.20	$13.20	$13.20
Purchase #3	$49.44	12.218%	$55.4806	$55.48	$55.50	$55.50
Purchase #4	$120.81	5.469%	$127.4171	$127.42	$127.40	$127.40
Purchase #5	$160.78	5.475%	$169.5827	$169.58	$169.60	$169.60
Purchase #6	$226.64	9.179%	$247.4433	$247.44	$247.45	$247.40
Purchase #7	$111.58	4.152%	$116.2128	$116.21	$116.20	$116.20
7 purchase totals =	$798.54		$853.2123	$853.21	$853.25	$853.20