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	$107.60	6.443%	$114.5327	$114.53	$114.55	$114.50
Purchase #2	$40.28	5.428%	$42.4664	$42.47	$42.45	$42.50
Purchase #3	$198.73	10.548%	$219.692	$219.69	$219.70	$219.70
Purchase #4	$75.39	10.573%	$83.361	$83.36	$83.35	$83.40
Purchase #5	$231.88	3.176%	$239.2445	$239.24	$239.25	$239.20
Purchase #6	$115.56	11.345%	$128.6703	$128.67	$128.65	$128.70
Purchase #7	$16.66	10.590%	$18.4243	$18.42	$18.40	$18.40
7 purchase totals =	$786.10		$846.3912	$846.38	$846.35	$846.40