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	$18.77	3.540%	$19.4345	$19.43	$19.45	$19.40
Purchase #2	$70.54	4.393%	$73.6388	$73.64	$73.65	$73.60
Purchase #3	$16.45	13.379%	$18.6508	$18.65	$18.65	$18.70
Purchase #4	$11.93	13.432%	$13.5324	$13.53	$13.55	$13.50
Purchase #5	$31.67	3.117%	$32.6572	$32.66	$32.65	$32.70
Purchase #6	$85.52	6.304%	$90.9112	$90.91	$90.90	$90.90
Purchase #7	$167.81	6.625%	$178.9274	$178.93	$178.95	$178.90
7 purchase totals =	$402.69		$427.7523	$427.75	$427.80	$427.70