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	$42.79	10.513%	$47.2885	$47.29	$47.30	$47.30
Purchase #2	$215.77	10.286%	$237.9641	$237.96	$237.95	$238.00
Purchase #3	$192.80	10.739%	$213.5048	$213.50	$213.50	$213.50
Purchase #4	$113.34	12.673%	$127.7036	$127.70	$127.70	$127.70
Purchase #5	$214.82	3.836%	$223.0605	$223.06	$223.05	$223.10
Purchase #6	$47.54	12.761%	$53.6066	$53.61	$53.60	$53.60
Purchase #7	$228.32	12.123%	$255.9992	$256.00	$256.00	$256.00
7 purchase totals =	$1,055.38		$1,159.1273	$1,159.12	$1,159.10	$1,159.20