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	$13.90	4.760%	$14.5616	$14.56	$14.55	$14.60
Purchase #2	$59.45	9.587%	$65.1495	$65.15	$65.15	$65.10
Purchase #3	$139.67	5.487%	$147.3337	$147.33	$147.35	$147.30
Purchase #4	$27.37	13.661%	$31.109	$31.11	$31.10	$31.10
Purchase #5	$156.59	5.425%	$165.085	$165.09	$165.10	$165.10
Purchase #6	$127.60	11.388%	$142.1311	$142.13	$142.15	$142.10
Purchase #7	$111.55	5.798%	$118.0177	$118.02	$118.00	$118.00
7 purchase totals =	$636.13		$683.3876	$683.39	$683.40	$683.30