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	$190.26	13.350%	$215.6597	$215.66	$215.65	$215.70
Purchase #2	$45.71	13.770%	$52.0043	$52.00	$52.00	$52.00
Purchase #3	$16.31	13.244%	$18.4701	$18.47	$18.45	$18.50
Purchase #4	$18.76	10.764%	$20.7793	$20.78	$20.80	$20.80
Purchase #5	$67.25	7.659%	$72.4007	$72.40	$72.40	$72.40
Purchase #6	$21.30	11.128%	$23.6703	$23.67	$23.65	$23.70
Purchase #7	$79.26	8.425%	$85.9377	$85.94	$85.95	$85.90
7 purchase totals =	$438.85		$488.9221	$488.92	$488.90	$489.00