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	$192.62	4.109%	$200.5348	$200.53	$200.55	$200.50
Purchase #2	$121.70	3.220%	$125.6187	$125.62	$125.60	$125.60
Purchase #3	$215.68	10.559%	$238.4537	$238.45	$238.45	$238.50
Purchase #4	$168.49	9.837%	$185.0644	$185.06	$185.05	$185.10
Purchase #5	$96.66	11.174%	$107.4608	$107.46	$107.45	$107.50
Purchase #6	$34.44	3.358%	$35.5965	$35.60	$35.60	$35.60
Purchase #7	$65.56	10.555%	$72.4799	$72.48	$72.50	$72.50
7 purchase totals =	$895.15		$965.2088	$965.20	$965.20	$965.30