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	$232.86	10.136%	$256.4627	$256.46	$256.45	$256.50
Purchase #2	$61.72	9.123%	$67.3507	$67.35	$67.35	$67.40
Purchase #3	$13.53	9.851%	$14.8628	$14.86	$14.85	$14.90
Purchase #4	$99.87	10.123%	$109.9798	$109.98	$110.00	$110.00
Purchase #5	$13.78	13.275%	$15.6093	$15.61	$15.60	$15.60
Purchase #6	$187.58	11.848%	$209.8045	$209.80	$209.80	$209.80
Purchase #7	$242.38	6.608%	$258.3965	$258.40	$258.40	$258.40
7 purchase totals =	$851.72		$932.4663	$932.46	$932.45	$932.60