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	$56.43	11.709%	$63.0374	$63.04	$63.05	$63.00
Purchase #2	$126.29	3.188%	$130.3161	$130.32	$130.30	$130.30
Purchase #3	$194.31	7.813%	$209.4914	$209.49	$209.50	$209.50
Purchase #4	$107.61	6.390%	$114.4863	$114.49	$114.50	$114.50
Purchase #5	$85.84	11.132%	$95.3957	$95.40	$95.40	$95.40
Purchase #6	$156.97	9.725%	$172.2353	$172.24	$172.25	$172.20
Purchase #7	$249.46	12.364%	$280.3032	$280.30	$280.30	$280.30
7 purchase totals =	$976.91		$1,065.2654	$1,065.28	$1,065.30	$1,065.20