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	$49.34	10.513%	$54.5271	$54.53	$54.55	$54.50
Purchase #2	$97.77	5.494%	$103.1415	$103.14	$103.15	$103.10
Purchase #3	$211.84	9.802%	$232.6046	$232.60	$232.60	$232.60
Purchase #4	$195.99	11.264%	$218.0663	$218.07	$218.05	$218.10
Purchase #5	$12.47	4.426%	$13.0219	$13.02	$13.00	$13.00
Purchase #6	$200.85	10.677%	$222.2948	$222.29	$222.30	$222.30
Purchase #7	$242.89	5.634%	$256.5744	$256.57	$256.55	$256.60
7 purchase totals =	$1,011.15		$1,100.2306	$1,100.22	$1,100.20	$1,100.20