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	$62.88	7.231%	$67.4269	$67.43	$67.45	$67.40
Purchase #2	$92.55	5.161%	$97.3265	$97.33	$97.35	$97.30
Purchase #3	$184.78	13.833%	$210.3406	$210.34	$210.35	$210.30
Purchase #4	$108.52	3.719%	$112.5559	$112.56	$112.55	$112.60
Purchase #5	$114.96	8.387%	$124.6017	$124.60	$124.60	$124.60
Purchase #6	$24.69	6.339%	$26.2551	$26.26	$26.25	$26.30
Purchase #7	$118.74	7.413%	$127.5422	$127.54	$127.55	$127.50
7 purchase totals =	$707.12		$766.0489	$766.06	$766.10	$766.00