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	$54.38	9.279%	$59.4259	$59.43	$59.45	$59.40
Purchase #2	$30.38	13.531%	$34.4907	$34.49	$34.50	$34.50
Purchase #3	$184.81	7.404%	$198.4933	$198.49	$198.50	$198.50
Purchase #4	$212.66	5.809%	$225.0134	$225.01	$225.00	$225.00
Purchase #5	$184.89	6.311%	$196.5584	$196.56	$196.55	$196.60
Purchase #6	$151.79	9.566%	$166.3102	$166.31	$166.30	$166.30
Purchase #7	$164.45	4.465%	$171.7927	$171.79	$171.80	$171.80
7 purchase totals =	$983.36		$1,052.0846	$1,052.08	$1,052.10	$1,052.10