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	$218.75	10.703%	$242.1628	$242.16	$242.15	$242.20
Purchase #2	$239.96	11.393%	$267.2986	$267.30	$267.30	$267.30
Purchase #3	$112.29	11.390%	$125.0798	$125.08	$125.10	$125.10
Purchase #4	$129.87	11.546%	$144.8648	$144.86	$144.85	$144.90
Purchase #5	$114.34	8.287%	$123.8154	$123.82	$123.80	$123.80
Purchase #6	$69.56	12.422%	$78.2007	$78.20	$78.20	$78.20
Purchase #7	$101.76	7.170%	$109.0562	$109.06	$109.05	$109.10
7 purchase totals =	$986.53		$1,090.4783	$1,090.48	$1,090.45	$1,090.60