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	$192.37	7.278%	$206.3707	$206.37	$206.35	$206.40
Purchase #2	$134.31	12.564%	$151.1847	$151.18	$151.20	$151.20
Purchase #3	$64.78	13.402%	$73.4618	$73.46	$73.45	$73.50
Purchase #4	$102.74	8.107%	$111.0691	$111.07	$111.05	$111.10
Purchase #5	$236.57	9.857%	$259.8887	$259.89	$259.90	$259.90
Purchase #6	$215.97	9.793%	$237.1199	$237.12	$237.10	$237.10
Purchase #7	$233.35	9.476%	$255.4622	$255.46	$255.45	$255.50
7 purchase totals =	$1,180.09		$1,294.5571	$1,294.55	$1,294.50	$1,294.70