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	$184.78	3.801%	$191.8035	$191.80	$191.80	$191.80
Purchase #2	$60.38	5.345%	$63.6073	$63.61	$63.60	$63.60
Purchase #3	$32.85	8.403%	$35.6104	$35.61	$35.60	$35.60
Purchase #4	$154.32	8.740%	$167.8076	$167.81	$167.80	$167.80
Purchase #5	$76.52	9.577%	$83.8483	$83.85	$83.85	$83.80
Purchase #6	$29.53	3.242%	$30.4874	$30.49	$30.50	$30.50
Purchase #7	$85.71	8.112%	$92.6628	$92.66	$92.65	$92.70
7 purchase totals =	$624.09		$665.8273	$665.83	$665.80	$665.80