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	$142.44	12.653%	$160.4629	$160.46	$160.45	$160.50
Purchase #2	$31.81	6.119%	$33.7565	$33.76	$33.75	$33.80
Purchase #3	$210.92	13.205%	$238.772	$238.77	$238.75	$238.80
Purchase #4	$71.61	11.789%	$80.0521	$80.05	$80.05	$80.10
Purchase #5	$166.70	11.404%	$185.7105	$185.71	$185.70	$185.70
Purchase #6	$144.76	4.286%	$150.9644	$150.96	$150.95	$151.00
Purchase #7	$239.34	8.847%	$260.5144	$260.51	$260.50	$260.50
7 purchase totals =	$1,007.58		$1,110.2328	$1,110.22	$1,110.15	$1,110.40