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	$205.60	4.663%	$215.1871	$215.19	$215.20	$215.20
Purchase #2	$240.25	10.721%	$266.0072	$266.01	$266.00	$266.00
Purchase #3	$33.88	7.514%	$36.4257	$36.43	$36.45	$36.40
Purchase #4	$31.52	8.846%	$34.3083	$34.31	$34.30	$34.30
Purchase #5	$168.47	13.392%	$191.0315	$191.03	$191.05	$191.00
Purchase #6	$56.32	12.531%	$63.3775	$63.38	$63.40	$63.40
Purchase #7	$209.46	11.289%	$233.1059	$233.11	$233.10	$233.10
7 purchase totals =	$945.50		$1,039.4432	$1,039.46	$1,039.50	$1,039.40