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	$210.90	5.443%	$222.3793	$222.38	$222.40	$222.40
Purchase #2	$27.37	6.111%	$29.0426	$29.04	$29.05	$29.00
Purchase #3	$217.61	8.382%	$235.8501	$235.85	$235.85	$235.90
Purchase #4	$225.38	12.490%	$253.53	$253.53	$253.55	$253.50
Purchase #5	$169.30	9.465%	$185.3242	$185.32	$185.30	$185.30
Purchase #6	$122.56	3.191%	$126.4709	$126.47	$126.45	$126.50
Purchase #7	$156.26	10.375%	$172.472	$172.47	$172.45	$172.50
7 purchase totals =	$1,129.38		$1,225.0691	$1,225.06	$1,225.05	$1,225.10