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	$239.66	9.810%	$263.1706	$263.17	$263.15	$263.20
Purchase #2	$96.30	4.387%	$100.5247	$100.52	$100.50	$100.50
Purchase #3	$205.77	9.351%	$225.0116	$225.01	$225.00	$225.00
Purchase #4	$179.47	3.186%	$185.1879	$185.19	$185.20	$185.20
Purchase #5	$201.34	9.464%	$220.3948	$220.39	$220.40	$220.40
Purchase #6	$25.45	4.385%	$26.566	$26.57	$26.55	$26.60
Purchase #7	$108.90	13.416%	$123.51	$123.51	$123.50	$123.50
7 purchase totals =	$1,056.89		$1,144.3656	$1,144.36	$1,144.30	$1,144.40