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	$160.45	7.425%	$172.3634	$172.36	$172.35	$172.40
Purchase #2	$43.78	7.812%	$47.2001	$47.20	$47.20	$47.20
Purchase #3	$134.34	10.195%	$148.036	$148.04	$148.05	$148.00
Purchase #4	$153.84	11.636%	$171.7408	$171.74	$171.75	$171.70
Purchase #5	$191.49	12.771%	$215.9452	$215.95	$215.95	$215.90
Purchase #6	$133.29	8.616%	$144.7743	$144.77	$144.75	$144.80
Purchase #7	$169.96	9.713%	$186.4682	$186.47	$186.45	$186.50
7 purchase totals =	$987.15		$1,086.5280	$1,086.53	$1,086.50	$1,086.50