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	$227.38	9.458%	$248.8856	$248.89	$248.90	$248.90
Purchase #2	$63.65	4.335%	$66.4092	$66.41	$66.40	$66.40
Purchase #3	$209.86	13.651%	$238.508	$238.51	$238.50	$238.50
Purchase #4	$206.75	12.838%	$233.2926	$233.29	$233.30	$233.30
Purchase #5	$85.62	11.238%	$95.242	$95.24	$95.25	$95.20
Purchase #6	$127.55	5.308%	$134.3204	$134.32	$134.30	$134.30
Purchase #7	$243.33	9.269%	$265.8843	$265.88	$265.90	$265.90
7 purchase totals =	$1,164.14		$1,282.5421	$1,282.54	$1,282.55	$1,282.50