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	$203.69	11.684%	$227.4891	$227.49	$227.50	$227.50
Purchase #2	$148.47	9.488%	$162.5568	$162.56	$162.55	$162.60
Purchase #3	$100.34	8.406%	$108.7746	$108.77	$108.75	$108.80
Purchase #4	$153.98	7.260%	$165.1589	$165.16	$165.15	$165.20
Purchase #5	$48.42	7.143%	$51.8786	$51.88	$51.90	$51.90
Purchase #6	$230.84	5.405%	$243.3169	$243.32	$243.30	$243.30
Purchase #7	$82.82	7.458%	$88.9967	$89.00	$89.00	$89.00
7 purchase totals =	$968.56		$1,048.1716	$1,048.18	$1,048.15	$1,048.30