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	$113.28	4.664%	$118.5634	$118.56	$118.55	$118.60
Purchase #2	$114.78	8.489%	$124.5237	$124.52	$124.50	$124.50
Purchase #3	$246.79	9.514%	$270.2696	$270.27	$270.25	$270.30
Purchase #4	$166.40	11.438%	$185.4328	$185.43	$185.45	$185.40
Purchase #5	$69.51	10.824%	$77.0338	$77.03	$77.05	$77.00
Purchase #6	$88.87	3.228%	$91.7387	$91.74	$91.75	$91.70
Purchase #7	$134.31	12.781%	$151.4762	$151.48	$151.50	$151.50
7 purchase totals =	$933.94		$1,019.0382	$1,019.03	$1,019.05	$1,019.00