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	$65.83	3.160%	$67.9102	$67.91	$67.90	$67.90
Purchase #2	$59.89	7.531%	$64.4003	$64.40	$64.40	$64.40
Purchase #3	$118.77	12.750%	$133.9132	$133.91	$133.90	$133.90
Purchase #4	$28.72	13.786%	$32.6793	$32.68	$32.70	$32.70
Purchase #5	$184.34	8.838%	$200.632	$200.63	$200.65	$200.60
Purchase #6	$107.77	7.436%	$115.7838	$115.78	$115.80	$115.80
Purchase #7	$185.93	4.588%	$194.4605	$194.46	$194.45	$194.50
7 purchase totals =	$751.25		$809.7793	$809.77	$809.80	$809.80