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	$197.79	9.144%	$215.8759	$215.88	$215.90	$215.90
Purchase #2	$169.82	12.467%	$190.9915	$190.99	$191.00	$191.00
Purchase #3	$34.56	12.304%	$38.8123	$38.81	$38.80	$38.80
Purchase #4	$112.58	12.376%	$126.5129	$126.51	$126.50	$126.50
Purchase #5	$54.37	9.187%	$59.365	$59.37	$59.35	$59.40
Purchase #6	$30.49	3.323%	$31.5032	$31.50	$31.50	$31.50
Purchase #7	$75.30	9.476%	$82.4354	$82.44	$82.45	$82.40
7 purchase totals =	$674.91		$745.4962	$745.50	$745.50	$745.50