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	$97.98	7.774%	$105.597	$105.60	$105.60	$105.60
Purchase #2	$128.39	13.395%	$145.5878	$145.59	$145.60	$145.60
Purchase #3	$61.86	12.659%	$69.6909	$69.69	$69.70	$69.70
Purchase #4	$91.25	12.558%	$102.7092	$102.71	$102.70	$102.70
Purchase #5	$133.39	6.502%	$142.063	$142.06	$142.05	$142.10
Purchase #6	$191.66	8.783%	$208.4935	$208.49	$208.50	$208.50
Purchase #7	$151.91	9.792%	$166.785	$166.79	$166.80	$166.80
7 purchase totals =	$856.44		$940.9264	$940.93	$940.95	$941.00