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	$61.92	12.763%	$69.8228	$69.82	$69.80	$69.80
Purchase #2	$27.45	4.196%	$28.6018	$28.60	$28.60	$28.60
Purchase #3	$35.83	13.678%	$40.7308	$40.73	$40.75	$40.70
Purchase #4	$104.99	8.636%	$114.0569	$114.06	$114.05	$114.10
Purchase #5	$164.25	9.456%	$179.7815	$179.78	$179.80	$179.80
Purchase #6	$110.61	9.790%	$121.4387	$121.44	$121.45	$121.40
Purchase #7	$105.47	6.687%	$112.5228	$112.52	$112.50	$112.50
7 purchase totals =	$610.52		$666.9553	$666.95	$666.95	$666.90