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	$79.78	6.871%	$85.2617	$85.26	$85.25	$85.30
Purchase #2	$179.92	6.460%	$191.5428	$191.54	$191.55	$191.50
Purchase #3	$54.30	12.613%	$61.1489	$61.15	$61.15	$61.10
Purchase #4	$95.29	4.264%	$99.3532	$99.35	$99.35	$99.40
Purchase #5	$99.87	9.383%	$109.2408	$109.24	$109.25	$109.20
Purchase #6	$230.71	3.758%	$239.3801	$239.38	$239.40	$239.40
Purchase #7	$235.63	10.345%	$260.0059	$260.01	$260.00	$260.00
7 purchase totals =	$975.50		$1,045.9334	$1,045.93	$1,045.95	$1,045.90