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	$84.92	3.144%	$87.5899	$87.59	$87.60	$87.60
Purchase #2	$234.89	5.359%	$247.4778	$247.48	$247.50	$247.50
Purchase #3	$19.36	6.145%	$20.5497	$20.55	$20.55	$20.50
Purchase #4	$42.55	6.806%	$45.446	$45.45	$45.45	$45.40
Purchase #5	$15.56	6.601%	$16.5871	$16.59	$16.60	$16.60
Purchase #6	$169.44	5.109%	$178.0967	$178.10	$178.10	$178.10
Purchase #7	$200.78	11.757%	$224.3857	$224.39	$224.40	$224.40
7 purchase totals =	$767.50		$820.1329	$820.15	$820.20	$820.10