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	$147.57	13.464%	$167.4388	$167.44	$167.45	$167.40
Purchase #2	$124.84	6.565%	$133.0357	$133.04	$133.05	$133.00
Purchase #3	$121.55	9.513%	$133.1131	$133.11	$133.10	$133.10
Purchase #4	$181.72	10.345%	$200.5189	$200.52	$200.50	$200.50
Purchase #5	$212.49	13.755%	$241.718	$241.72	$241.70	$241.70
Purchase #6	$75.61	9.475%	$82.774	$82.77	$82.75	$82.80
Purchase #7	$191.79	4.412%	$200.2518	$200.25	$200.25	$200.30
7 purchase totals =	$1,055.57		$1,158.8503	$1,158.85	$1,158.80	$1,158.80