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	$76.50	6.486%	$81.4618	$81.46	$81.45	$81.50
Purchase #2	$101.25	10.269%	$111.6474	$111.65	$111.65	$111.60
Purchase #3	$122.32	9.192%	$133.5637	$133.56	$133.55	$133.60
Purchase #4	$232.93	6.695%	$248.5247	$248.52	$248.50	$248.50
Purchase #5	$188.58	4.771%	$197.5772	$197.58	$197.60	$197.60
Purchase #6	$41.44	3.548%	$42.9103	$42.91	$42.90	$42.90
Purchase #7	$241.90	7.842%	$260.8698	$260.87	$260.85	$260.90
7 purchase totals =	$1,004.92		$1,076.5549	$1,076.55	$1,076.50	$1,076.60