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	$147.95	11.522%	$164.9968	$165.00	$165.00	$165.00
Purchase #2	$12.43	5.384%	$13.0992	$13.10	$13.10	$13.10
Purchase #3	$17.67	13.606%	$20.0742	$20.07	$20.05	$20.10
Purchase #4	$200.73	13.107%	$227.0397	$227.04	$227.05	$227.00
Purchase #5	$169.88	11.564%	$189.5249	$189.52	$189.50	$189.50
Purchase #6	$41.43	12.411%	$46.5719	$46.57	$46.55	$46.60
Purchase #7	$42.52	7.243%	$45.5997	$45.60	$45.60	$45.60
7 purchase totals =	$632.61		$706.9064	$706.90	$706.85	$706.90